The effect of leadless pacing on LV and RV systolic function is not inferior to conventional RV pacing

Introduction

Leadless right ventricular (RV) pacing has been recently proposed as alternative to conventional pacemakers (PM's). While RV pacing with a conventional PM is known to cause deterioration of left ventricular (LV) and RV systolic function over time, the effects of leadless PM's are currently under-explored. In this prospective and randomized study, we hypothesized that the effect of leadless RV pacing over time on both LV and RV systolic function is not inferior to conventional RV pacing.

Methods

Fifty-one age-matched patients with a guideline indication for a PM were prospectively recruited and randomized to undergo implantation of either (i) a leadless PM, or (ii) a conventional PM. Patients underwent echocardiography prior to (BL), and at 6 and 12 months (M6 & M12) after PM implantation. All imaging after implantation was performed during active pacing. Analysis included LV ejection fraction (LVEF), LV global longitudinal strain (GLS), and RV free wall (FW) strain.

Results

Twenty-seven patients were implanted with a leadless PM, while twenty-four received a conventional PM. Median age was 82 (80–87) years. At BL, average LVEF and LV GLS were normal and similar in both groups. At M12, both LVEF (−12%) and LV GLS strain (−5%) decreased significantly in both study groups (ANOVA p<0.0001, see Figure 1). RV FW strain decreased only significantly in patients with conventional PM (−4%; ANOVA p=0.031, see Figure 1; post-hoc test BL vs. M12: p=0.029). None of the tested variables, at none of the time points, showed significant difference between the leadless and conventional PM study groups (all p>0.05). Median pacing percentage was 68.2% and similar in both study groups (at all time-points p>0.05).

Conclusions

Both patients with leadless and conventional PM's demonstrate a decrease in LV and RV systolic function, 12 months after implantation. While LV function decrease was similar between both groups, RV function decrease was most prominent in patients treated with conventional PM's. Our data suggest that leadless pacing is not inferior to conventional pacing with regard to the effect on cardiac function.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Research Foundation Flanders (FWO) post-doc grant

Predictors of shear wave propagation speed assessed by shear wave elastography

Background

Cardiac shear wave elastography (SWE) is a novel ultrasound-based method that assesses the propagation speed of shear waves travelling in the myocardium induced by e.g. mitral valve closure (MVC). The propagation speed of these waves is related to the stiffness of the myocardium. The capability of SWE to evaluate myocardial stiffness has already been demonstrated in several publications. However, which factors beside the intrinsic mechanical properties of the myocardium influence shear wave speed in vivo has not been extensively investigated.

Purpose

The aim of this study was to investigate the influence of clinical parameters as well as echocardiographic indicators of myocardial tissue properties and left ventricular (LV) filling pressures on shear wave propagation speed after MVC.

Methods

219 subjects (59±17 years; 140 males) were included in the study. Of those, 49 were healthy volunteers, 25 were patients with cardiac amyloidosis, 42 with hypertrophic cardiomyopathy, 35 with hypertensive heart disease and 68 with coronary artery disease. Subjects were scanned with an experimental ultrasound scanner using diverging wave imaging to acquire images at a high temporal resolution (average frame rate: 1167±414 Hz). Shear waves after MVC were visualized on M-mode maps along the interventricular septum which were colour coded for tissue acceleration (Figure 1). The propagation speed was calculated by semi-automatically measuring the spatiotemporal slope of the shear wave. Univariate and multivariate linear regression analysis was performed to identify variables associated with shear wave propagation speed.

Results

Univariate regression analysis revealed an association of the following variables with shear wave speed: age, BMI, systolic blood pressure, E wave, average e', E/e', left atrial volume index (LAVI), grade of diastolic dysfunction, isovolumic relaxation time, septal wall thickness, LV wall mass and presence of cardiomyopathy. These variables were added to a multivariate model. Predictors of shear wave speed after MVC were BMI, E wave, average e', LAVI, LV wall mass and presence of cardiomyopathy (R2=0.53) (Table 1).

Conclusions

The results of this study indicate that both myocardial structural properties (reflected by predictors LV wall mass and presence of cardiomyopathy) and LV filling pressures (reflected by predictors E wave, average e' and LAVI) affect shear wave speed. These findings suggest that SWE has the potential to assess structural as well as functional changes to the LV, which should be further explored.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research foundation Flanders - FWO

Resynchronization of the left atrium may play an important role in cardiac resynchronization therapy

Introduction

Left atrial (LA) dyssynchrony is a predictor of response to cardiac resynchronization therapy (CRT). It is unknown, however, if LA resynchronization contributes to response to CRT. We hypothesize that there is a relationship between correction of LA dyssynchrony and response to CRT.

Purpose

To investigate the association between LA resynchronization and response to CRT.

Methods

In a prospective study of 171 heart failure patients with LBBB, myocardial strain was measured by speckle-tracking echocardiography, before and 6 months after CRT. As indicated by the white arrows in Figure 1, LA dyssynchrony was measured as the time delay between onset systolic stretch of the interatrial septum and the LA lateral wall. Response to CRT was defined as at least 15% reduction in left ventricular (LV) end systolic volume at 6 months follow up.

Results

119 (70%) patients responded to CRT. The panels in Figure 1 shows LA strain traces in a representative LBBB patient that did respond (upper panels), and a patient that did not respond (lower panels). The white arrows in the left panels indicate that both the responder and the non-responder had marked LA dyssynchrony before CRT (198 and 171 ms, respectively). However, after 6 months with CRT, there was recovery of LA synchrony only in the responder (time delay −40 ms), and still marked LA dyssynchrony of 191 ms in the non-responder (right panels).

Figure 2 confirms similar results for the whole study population: CRT response was associated with marked reduction of LA dyssynchrony (p=0.0001). In the CRT non-responders there was, however, only a modest, non-significant reduction of LA dyssynchrony.

Conclusions

Positive CRT response was associated with resynchronization of the left atrium. These findings suggest LA resynchronization as a potential additional target for CRT.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Institute for Surgical Research, Oslo University HospitalThe Intervention Centre, Oslo University Hospital

Sequential left ventricular electro-mechanical changes in left bundle branch pacing vs right ventricular pacing a two-center study

Background

Left bundle branch pacing (LBBP) has been proved to maintain electrical synchrony better than RVP during mid to long-term follow-up, but little is known about the left ventricular (LV) mechanical changes over time. This study investigates if LBBP causes less sequential electro-mechanical alterations in LV that develop over time, compared with both conventional (CRVP) and leadless (LRVP) RVP.

Methods

Sixty-five patients with pacing indication for bradycardia were prospectively enrolled: Twenty-two were treated with LBBP, 23 with CRVP and 20 with LRVP. QRS duration (QRSd) was measured at baseline and during follow-up. All patients underwent echocardiography at baseline, one week after implantation and at one-year follow-up. LV volumes, ejection fraction (EF) and global longitudinal strain (GLS) were measured. Septal flash (SF), apical rocking and septal longitudinal strain patterns were assessed visually by two experienced readers.

Results

All the patients presented with normal strain pattern and no signs of SF or apical rocking at baseline. 100% of CRVP and 95% of LRVP patients had stage1 or 2 septal deformation patterns at week 1, and the majority (72.3% CRVP and 83.3% LRVP) progressed to stage≥2 at 12 months. On the contrary, over 2/3 of LBBP patients preserved normal strain patterns at week 1, and less than 1/3 had stage-1 pattern, 2 out of whom progressed to stage-2 during follow-up (Figure 1). At week 1 and 12 months, all RVP patients had SF, and most of them also exhibited apical rocking (87%-94.4% in CRVP and 80%-94.4% in LRVP). However, much less septal flash and apical rocking was induced in LBBP patients at week 1 and last follow-up (27.3%-37.5% and 22.7%-25%, P<0.001 vs RVP). Baseline QRSd were similar among three groups. At week 1, the paced QRSd increased least in LBBP compared to CRVP and LRVP and remained as such at 12 months. During one year follow-up, LVEF and LV GLS decreased more in CRVP group compared to LBBP (both P<0.05) (Figure 2).

Conclusion

LBBP causes less sequential changes in LV deformation patterns, septal flash and apical rocking, compared to CRVP and LRVP. With this, LBBP appears to preserve LV function better than RVP. CRVP and LRVP did not differ in electro-mechanical changes or LV remodeling.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders (FWO) project grant

Can echocardiography facilitate decision-making to CRT?

Introduction

Cardiac resynchronization therapy (CRT) remains underused despite its well-established therapeutic effect and clear guidelines. Among various reasons are the lack of referral, the fear of complications and the high therapy cost. The assessment of mechanical dyssynchrony (MD) on echocardiography has been suggested to aid patient selection. In the past, however, several studies have used old markers of MD producing disappointing results and the use of echocardiography for patient selection became discredited. Promising new markers have been developed since and could aid clinical decision-making for CRT. These should, however, first be thoroughly tested and compared to the old markers.

Purpose

(I) To confirm the relevance of the new markers of MD for survival free of cardiac death and (II) to compare old and new markers of MD for predicting cardiac death within 5 years post-CRT in patients eligible for CRT according the 2021 ESC guidelines.

Methods

222 CRT-patients were analysed retrospectively in a multicentre setting. MD was assessed using three old markers: septal-to-posterior wall-motion-delay (SPWMD), left-ventricular-filling-time/cardiac-cycle ratio (LVFT/RR), and intraventricular mechanical delay (IVMD); and three new markers: systolic stretch index (SSI), myocardial work index (MWI), and visual presence of septal flash or apical rocking (SFoAR). For each marker, patients were categorized using previously published cut-offs as “MD present” (Yes) or “MD not present” (No). Log rank tests were performed on Kaplan-Meier curves for survival free of cardiac death. Cox proportional hazards regressions were used to compute the hazard-ratio (HR) for cardiac death within 5 years after implantation.

Results

Cardiac death occurred in 37 patients (17%). Patients with MD before CRT according to IVMD (p=0.003), SSI (p<0.001), MWI (p<0.001) or SFoAR (p<0.001) had a significantly better survival. The hazard ratios were 0.34 (95% CI, 0.19–0.75) for IVMD, 0.30 (95% CI, 0.15–0.57) for SSI, 0.26 (95% CI, 0.12–0.54) for MWI and, 0.28 (95% CI, 0.14–0.53) for SFoAR. The other markers for MD were not significant for survival.

Conclusion

The new markers for dyssynchrony are better than the old. Patients with mechanical dyssynchrony on echocardiography before CRT according to SSI, MWI or SFoAR are 3 to 4 times less likely to die within 5 years after CRT implantation. The presence of one of these markers in patients with a broad QRS (≥130ms) and reduced LVEF (≤35%) should prompt clinicians to refer for or to proceed to CRT.

Funding Acknowledgement

Type of funding sources: None.

Reintroducing dyssynchrony significantly increases myocardial stiffness at mitral valve closure

Background

Cardiac shear wave elastography (SWE) allows for the non-invasive assessment of myocardial stiffness via the detection of shear waves. Shear waves are mechanical waves that travel through the heart after for example mitral valve closure (MVC). The propagation speed of these waves is directly dependent on myocardial stiffness, where a higher shear wave speed correlates with a higher stiffness. However, the effect of a left bundle branch block (LBBB) and a dyssynchronous contraction pattern on shear wave speed is currently unknown.

Purpose

To investigate the effect of a dyssynchronous contraction pattern caused by LBBB on shear wave speed.

Methods

We included 29 non-ischemic heart failure patients with an LBBB (68±15y; 52% males) and 9 age-matched healthy volunteers (68±4y; 55% males) as controls. All LBBB patients were implanted with a CRT device and dyssynchrony was reintroduced by turning biventricular (BiV) pacing off to allow native ventricular conduction. Echocardiographic images were taken during BiV pacing on and BiV pacing off, with a conventional ultrasound machine and an experimental high frame rate ultrasound scanner. Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed. Further, longitudinal strain at MVC and the time difference between onset of septal contraction and MVC were measured (negative time values indicate that MVC occurs before onset of septal contraction).

Results

There was no significant difference in shear wave speed between healthy controls and LBBB patients during BiV pacing on (4.5±1.1 m/s vs 4.9±1.2 m/s; p=0.365; Figure A). However, shear wave speed was significantly higher in LBBB patients during BiV pacing off compared to healthy controls (4.5±1.1 m/s vs 5.6±1.1 m/s; p=0.041; Figure A). Turning BiV pacing off lead to a significant increase in shear wave speed in LBBB patients (4.9±1.2 m/s vs 5.6±1.1 m/s; p=0.003; Figure A), indicating that the reintroduction of LBBB increases septal myocardial stiffness. MVC occurred significantly later after the onset of septal contraction during BiV pacing off (−9±57 ms vs 40±26 ms; p=0.001) and strain values at MVC were more negative (−0.3±0.6% vs −2.0±1.5%; p<0.001). Therefore we hypothesize that during BiV pacing off, the septal wall was further into the contraction phase at the time of MVC, leading to an increased myocardial stiffness, and thus increased shear wave speed (Figure B). Our interpretation was further strengthened by a strong correlation between the change in shear wave speed and the change in septal longitudinal strain at MVC when BiV pacing is turned off (r=0.81; p<0.001; Figure C).

Conclusion

Reintroducing dyssynchrony in LBBB patients significantly increases shear wave speed at MVC. Our results suggest that the earlier contraction of the septum during dyssynchrony is an explanation for the higher septal stiffness at MVC.

Funding Acknowledgement

Type of funding sources: None.

Cardiac shear wave elastography can detect the presence of a septal scar in patients with LBBB

Background

In patients with heart failure and a left bundle branch block (LBBB), cardiac resynchronization therapy (CRT) is an established treatment. However, the rate of non-response to this costly therapy remains high. So far, CRT has proven to be less effective in patients with a septal scar. Detection of a septal scar before CRT implantation could therefore help to improve response rate to CRT. The gold standard to detect septal scarring, LGE MRI, is quite costly and not suited or available for all patients. Cardiac shear wave elastography (SWE) may be an alternative. It allows for the non-invasive assessment of myocardial stiffness based on the detection of shear waves, after for example mitral valve closure (MVC). SWE has shown to be capable to detect myocardial scar, however this has never been demonstrated in the presence of LBBB.

Purpose

To determine whether SWE is able to detect the presence of a septal scar in patients with LBBB.

Methods

To investigate this, 39 CRT patients with a LBBB were included with ischemic (n=10; age: 73±6 y; 70% males) or non-ischemic (n=29; 68±14 y; 52% males) cardiomyopathy and 9 age-matched healthy volunteers (68±4 y; 55% males) served as controls. In order to obtain native ventricular conduction biventricular (BiV) pacing was turned off. All ischemic patients had septal scar only, proven by MRI or scintigraphy. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (frame rate: 932±32 fps). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure 1A).

Results

Patients characteristics and echocardiographic parameters are shown in Table 1. Shear wave speed after MVC was significantly higher in LBBB patients with and without a septal scar compared to healthy controls (7.8±1.2 m/s vs 4.5±1.1 m/s; p<0.001; 5.6±1.1 m/s vs 4.5±1.1 m/s; p=0.041; Figure 1B), indicating that the presence of LBBB increases myocardial stiffness. However, more importantly, shear wave speed was significantly higher in LBBB patients with a septal scar compared to LBBB patients without a septal scar (7.8±1.2 m/s vs 5.6±1.1 m/s; p<0.001; Figure 1B). This implies that the presence of a septal scar increases shear wave speed even more than LBBB alone. A ROC-curve analysis further showed that SWE is capable of distinguishing scarred from non-scarred septum in LBBB patients (AUC: 0.92; p<0.001; Figure 1C). A cut-off of 7.1 m/s could identify LBBB patients with a septal scar with a sensitivity of 80% and specificity of 93%.

Conclusion

Septal scarring results in a significant increase in myocardial stiffness, so that it reaches a clear pathological range. SWE seems therefore capable of detecting the presence of a septal scar in LBBB patients and could potentially be used as a novel approach for the assessment of septal scarring in CRT candidates.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research foundation Flanders (FWO)

Left bundle branch pacing is superior in preserving ventricular mechanical synchrony and cardiac function than right ventricular pacing: a two-center experience

Background

Left bundle branch pacing (LBBP) has emerged as a novel pacing modality. Although it has been proved to maintain electrical synchrony better than right ventricular pacing (RVP), little is known about the impact on mechanical synchrony. This study investigates if LBBP preserves mechanical synchrony and cardiac function better compared to conventional (CRVP) and leadless (LRVP) RVP.

Methods

Sixty-five patients with pacing indication for bradycardia were prospectively enrolled: Twenty-two were treated with LBBP, 23 with CRVP and 20 with LRVP. All patients underwent echocardiography before and after implantation and at one-year follow-up. Left ventricular (LV) volumes, ejection fraction (EF) and global longitudinal strain (GLS) were measured. Regional septal (SW) and lateral wall work (LW) was calculated as the average from the respective basal and mid-ventricular segments in the apical four-chamber and three-chamber view. The lateral-septal work difference (LSWD) was used as a measure of mechanical dyssynchrony.

Results

At baseline, the QRS duration and LSWD were similar in all three groups. During follow-up, the QRS duration increased least in LBBP compared to CRVP and LRVP (+28.1±18.3ms vs +58.2±31.4 and 47.1±26.1ms, both P<0.01). SW was markedly decreased in CRVP and LRVP while LW work remained unchanged, resulting in a large LSWD compared to LBBP (1308.4±732.9 mmHg*% and 1451.3±606.1 mmHg*% vs. 286.0±479.9mmHg*%, both P<0.001). During one year follow-up, LVEF and LV GLS decreased more in CRVP compared to LBBP (both P<0.05).

Conclusion

LBBP causes less LV dyssynchrony than CRVP and LRVP as it preserves a more physiologic conduction pattern. With this, LBBP appears to preserve LV function better than CRVP. CRVP and LRVP did not differ in mechanical dyssynchrony or LV remodelling.

Funding Acknowledgement

Type of funding sources: None.

Left bundle branch pacing preserves ventricular mechanical synchrony better than right ventricular pacing-a two-center study

Funding Acknowledgements

Type of funding sources: None.

Background

Left bundle branch pacing (LBBP) has emerged as a novel pacing method. We sought to evaluate left ventricular (LV) mechanical synchrony under permanent LBBP and compare it with conventional and leadless right ventricular pacing (CRVP, LRVP).

Methods

Sixty-four patients with pacing indication for bradycardia were prospectively enrolled. Twenty-two patients received LBBP in the basal ventricular septum. Twenty-three patients received CRVP and 19 LRVP. All patients underwent echocardiography before and after device implantation. Myocardial work was estimated by pressure-strain analysis. Regional work in the septum (SEP) and lateral wall (LW) was calculated as the average from the respective basal and mid-ventricular segments in the apical four-chamber and three-chamber view. The absolute difference between work in LW and SEP (LW-S-work difference) was used as a measure of asymmetry in workload.

Results

Baseline characteristics were similar among the three groups. The electrocardiogram during LBBP showed a right bundle branch block pattern; during CRVP and LRVP a left bundle branch block pattern. The paced QRS duration was 114.27±9.9 ms in the LBBP group, significantly shorter than that in the CRVP and LRVP groups (153.9±25.26 ms and 159.1±13.99ms, respectively, both p<0.001). The SEP work decreased in all groups during ventricular pacing (all P<0.05), while the LW work remained similar. The paced LW-S work difference and work difference change between pacing on and off were more significant in the CRVP (1012.9±566.0mmHg*%) and LRVP group (1066.1±472.6mmHg*%) than the LBBP group (260.5±239.8mmHg*%, both P<0.001). In addition, LW-S work difference during ventricular pacing and work difference change between pacing and baseline were comparable in CRVP and LRVP group.

Conclusion

LBBP causes less LV dyssynchrony than CRVP and LRVP as it preserves a more physiologic conduction pattern. CRVP and LRVP did not differ in this respect. Further studies need to prove that LBBP has advantages over RVP with regards to preservation of LV synchrony and contractility.

Progressive left ventricular electro-mechanical remodelling in presence of left bundle branch block

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders (FWO)

Introduction

Recent cross-sectional studies suggest a relationship between persisting left bundle branch block (LBBB) and the extent of left ventricular (LV) electro-mechanical remodelling over time. However, when patients are referred for cardiac resynchronization therapy (CRT), temporal data during the sub-clinical phase of disease are often missing. A longitudinal study using an animal model would improve our understanding of the relationship between the onset of LBBB and the electro-mechanical remodelling.

Purpose

To investigate the progressive remodelling that develops over time in an animal model of LBBB.

Methods

Fifteen sheep were subjected to rapid DDD pacing (180 bpm; leads on right atrium and right ventricular free wall) in order to induce a LBBB-like conduction delay. All animals underwent an 8-week pacing protocol, whereas 5 of them were subjected to 16 weeks of pacing in total. Echocardiographic speckle tracking was used to assess circumferential strain of the septal and lateral wall. Septal and lateral wall thickness were measured at end-diastole. Cardiac magnetic resonance imaging was used to determine LV volumes and ejection fraction (LVEF). Examinations took place at baseline (before and after start of pacing), and after 8 and 16 weeks of pacing. All examinations were performed at a physiologic heart rate of 110 bpm.

Results

At baseline, DDD pacing induced an increase in QRS duration (+83%, p < 0.0001) and LBBB-like mechanical dyssynchrony, with mild early-systolic notching and preserved systolic shortening of the septal wall. Early lateral wall pre-stretch was followed by increasing systolic shortening. No acute changes in LV end-diastolic volume, LVEF or septal or lateral wall thickness were observed (all p > 0.05). After 8 weeks of DDD pacing, mechanical dyssynchrony worsened: septal notching increased, followed by reduced systolic shortening. After 16 weeks, the initial septal shortening was followed by profound stretching throughout systole. Lateral wall shortening was reduced compared to baseline (p < 0.05). QRS duration progressively increased by +15% (week 8) and +26% (week 16) (all p < 0.001). End-diastolic volumes had increased by +38% (week 8) and +74% (week 16), whereas LVEF had decreased by –35% (week 8) and –55% (week 16) (all p < 0.001). Septal wall thickness had reduced by –18% (week 8) and –29% (week 16), while lateral wall thickness had increased by +13% (week 8) and +24% (week 16) (all p < 0.05).

Conclusion

A persisting LBBB induces progressive changes in LV deformation patterns, and triggers morphological and electrical remodelling, strengthening the concept of LBBB-induced cardiomyopathy. In the clinic, patients with mild dysfunction should be closely monitored for potential disease progression in order to treat dyssynchrony as soon as guideline indications are reached. Further studies need to show if earlier CRT-implantation might prevent further LV deterioration. Abstract Figure.  Abstract Figure.

Combined assessment of septal scar and septal flash by cardiac magnetic resonance identifies responders to cardiac resynchronization therapy

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): South-Eastern Norway Regional Health Authority. Research grants of the University of Leuven.

Background

Left ventricular (LV) scar, particularly in the lateral wall and septum, reduces response rate to cardiac resynchronization therapy (CRT), whereas a dyssynchronous LV contraction pattern (septal flash) suggests good response. Lateral wall scar abolishes septal flash. Therefore, a combined approach of septal scar and septal flash may characterize the myocardial substrate responsive to CRT. Cardiac magnetic resonance (CMR) may assess both scar and contraction pattern.

Purpose

The present study aimed to determine if combined assessment of septal scar and septal flash by CMR as single image modality identifies responders to CRT.

Methods

We investigated all CRT recipients with available CMR from a prospective, multicenter study (n = 136), with both ischemic and non-ischemic heart failure. Septal scar was assessed by late gadolinium enhancement (LGE) from a stack of short axis slices (n = 128) and septal flash determined visually on ordinary cine sequences (n = 136). CRT response was defined as ≥15% reduction in LV end-systolic volume by echocardiography at 6 months follow-up. We also assessed heart transplantation or death of any cause 39 ± 13 months after device implantation.

Results

In multivariate analysis including percentage septal scar (LGE), septal flash, QRS-duration and QRS-morphology, septal LGE and septal flash were the only independent predictors of CRT response (both p < 0.001). A combined approach of septal LGE and septal flash predicted CRT response with area under the curve 0.86 (95% confidence interval (CI): 0.78-0.94) and long-term survival without heart transplantation with hazard ratio 0.18 (95% CI: 0.05-0.61).

A practical approach to selection of CRT candidates by septal LGE and septal flash is illustrated in the present figure. As shown, absence of septal LGE indicated excellent response rate (93%) to CRT independent of other parameters. When septal LGE was present, however, overall response rate was substantially lower (58%), but presence or absence of septal flash separated responders from non-responders with high accuracy. This sequential approach correctly classified 86% of patients. Importantly, the approach was equally accurate in patients with intermediate QRS duration (130-150ms), where 93% of patients were correctly classified.

Conclusions

Combined assessment of septal LGE and septal flash by CMR as single image modality identifies CRT responders with high accuracy and predicts long-term survival. Abstract Figure.

Systolic shear wave propagation speed as a novel non-invasive marker of myocardial contractility

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders - FWO

Background

Shear wave elastography is a novel echocardiographic method that tracks shear wave propagation in the cardiac wall using high frame rate ultrasound. Shear waves can be induced by e.g. aortic valve closure (AVC). The propagation speed of these waves is related to the stiffness of the myocardium. Previous work has suggested that systolic shear wave speed is related to myocardial contractility. The current gold standard reference method for the evaluation of left ventricular (LV) contractility is pressure-volume loop analysis. However, the invasive nature of this method limits its clinical applicability.

Purpose

To compare non-invasively assessed shear wave propagation speed after AVC to invasive pressure-volume loop-derived measurements of contractility.

Methods

In 12 pigs (31.9 ± 4.3 kg), dobutamine was administered intravenously. Conventional and high frame rate echocardiographic images were acquired simultaneously with invasively measured pressure-volume loops before and after the administration of dobutamine. High frame rate echocardiographic datasets were acquired with an experimental ultrasound scanner at an average frame rate of 1304 ± 115 frames per second. Shear waves after AVC were visualized on M-mode displays along the interventricular septum which were colour coded for tissue acceleration (Figure 1A). The propagation speed was calculated by semi-automatically measuring the spatiotemporal slope of the shear wave. A set of pressure-volume loops were acquired during preload reduction by balloon occlusion of the vena cava inferior. The end-systolic elastance (Ees) of the ESPVR and preload recruitable stroke work (PRSW) were used as measures of contractility.

Results

Heart rate (72 ± 20 bpm vs. 105 ± 25 bpm; p < 0.05) and LV ejection fraction (61 ± 4% vs. 74 ± 7%; p < 0.001) significantly increased after the administration of dobutamine, while the LV end-systolic pressure remained similar (92 ± 21 mmHg vs. 106 ± 23 mmHg; p = 0.08). Pressure-volume loop-derived measures of contractility increased during dobutamine infusion (Ees: 1.3 ± 0.5 mmHg/ml vs. 2.1 ±  1.0 mmHg/ml; p < 0.01 and PRSW: 41 ± 25 mmHg vs. 86 ± 23 mmHg; p < 0.01). Likewise, shear wave propagation speed after AVC increased after dobutamine administration compared to baseline (3.1 ± 0.6 m/s vs. 5.3 ± 1.1 m/s; p < 0.001). Shear wave speed after AVC had a strong positive correlation with Ees (r = 0.68; p < 0.001) (Figure 1B) and PRSW (r = 0.65; p = 0.001) (Figure 1C).

Conclusions

Systolic shear wave propagation speed is related to invasively determined measurements of LV contractility. The results of this study indicate the potential of shear wave speed after AVC as a novel non-invasive parameter for the assessment of LV contractile function. Abstract Figure.

Dyssynchrony significantly increases myocardial stiffness at mitral valve closure

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO: Fonds Wetenschappelijk Onderzoek (fund for Scientific Research Flanders)

Background

Recently, shear wave elastography (SWE) has emerged as a promising, non-invasive technique to determine myocardial tissue stiffness. SWE is based on the detection of shear waves, for example induced by mitral valve closure (MVC), that propagate through the myocardium. The propagation speed of these shear waves is directly dependent on myocardial stiffness. However, the effect of a dyssynchronous contraction pattern – as it occurs in left bundle branch block (LBBB) – on shear wave speed is currently unknown.

Purpose

To investigate the effect of the dyssynchronous contraction pattern caused by LBBB on shear wave speed.

Methods

We included 25 non-ischemic heart failure patients with LBBB (age: 68 ± 15y; 52% males), all implanted with a CRT device. Dyssynchrony was reintroduced by turning biventricular (BiV) pacing off to allow native ventricular conduction. Echocardiographic images were taken during BiV pacing on and BiV pacing off, both with a conventional ultrasound machine and an experimental high frame rate ultrasound scanner (frame rate: 932 ± 32 fps). For SWE, left ventricular parasternal long-axis views were acquired. Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed. Speckle tracking of the four-chamber apical view was used to asses longitudinal strain of the mid-septal segment. To further investigate how dyssynchrony affects shear wave speed, the following time points were measured: onset of QRS, MVC and onset of septal contraction.

Results

Acutely switching BiV pacing on and off did not significantly affect left ventricular ejection fraction, nor end-diastolic or end-systolic volumes (all p > 0.05). Shear wave speed was significantly higher during BiV pacing off compared to BiV pacing on (5.6 ± 1.2 m/s vs 4.9 ± 1.3 m/s; p = 0.003; figure A). Furthermore, the onset of septal contraction was significantly earlier during BiV off (11 ± 15 ms vs 105 ± 57 ms; p < 0.0001). As a result, during BiV pacing off, the septal wall was further into the contraction phase at the time of MVC, leading to an increased myocardial stiffness, and thus increased shear wave speed (figure B). Our interpretation that increased shear wave speed could be attributed to an earlier onset of contraction of the septum was further strengthened by a strong correlation between the change in shear wave speed and the change in septal longitudinal strain at MVC when BiV pacing is turned off (r = 0.83; p < 0.001; figure C).

Conclusion

A dyssynchronous contraction caused by LBBB significantly increases shear wave propagation speed at MVC. This could be attributed to the early-systolic contraction of the septum during dyssynchrony. These results indicate that changes in contraction pattern caused by LBBB significantly influence myocardial stiffness at MVC. Abstract Figure.

Myocardial stiffness assessed by shear wave elastography relates to pressure-volume loop derived measurements of chamber stiffness

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundations Flanders

Background

Increased myocardial stiffness is an important cause of diastolic dysfunction. Currently, invasive pressure-volume loop analysis is the gold standard method for the assessment of the left ventricular (LV) chamber stiffness. Its non-invasive assessment in the clinic is cumbersome, requires the combination of several parameters and has limited reliability. Shear wave elastography (SWE) is a novel method that evaluates the propagation of shear waves travelling along the myocardium using high frame rate echocardiography. The propagation speed is directly related to myocardial stiffness. Shear waves can be induced naturally by mitral valve closure (MVC). So far, the in vivo validation of SWE against an invasive gold standard reference method is still lacking.

Purpose

To compare myocardial stiffness assessed by shear wave propagation speed after MVC to invasive pressure-volume loop derived measurements of chamber stiffness.

Methods

Fifteen pigs (31.2 ± 4.1 kg) were included in the study. The instantaneous stiffness of the myocardium was altered by performing the following interventions: 1) preload reduction, 2) afterload increase, 3) preload increase and 4) induction of ischemia/reperfusion (I/R) injury by balloon occlusion of the proximal LAD for 90 min. with subsequent reperfusion of 40 min. To obtain the end-diastolic pressure-volume loop relation (EDPVR), a set of pressure-volume loops was acquired under preload reduction. From the EDPVR, the chamber stiffness constant β and operating chamber stiffness dP/dV were derived. SWE datasets in a parasternal long-axis view were acquired with an experimental ultrasound scanner at an average frame rate of 1304 ± 115 Hz. Shear waves after MVC were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum (Figure 1A). The propagation speed was calculated by semi-automatically measuring the spatiotemporal slope.

Results

The chamber stiffness constant β significantly increased after the induction of the I/R injury (0.05 ± 0.01 1/ml vs. 0.09 ± 0.03 1/ml; p < 0.001). The operating chamber stiffness dP/dV decreased by reducing preload and increased by increasing afterload, increasing preload or by inducing an I/R injury (0.50 ± 0.18 mmHg/ml vs. 0.09 ± 0.05 mmHg/ml, 0.67 ± 0.19 mmHg/ml, 0.78 ± 0.35 mmHg/ml and 1.09 ± 0.38 mmHg/ml, respectively; p < 0.01). Likewise, shear wave propagation speed after MVC increased by increasing pre- and afterload (p = 0.001) and by inducing I/R injury (p < 0.001) (Figure 1B). Preload reduction had no significant influence (p = 0.118). Shear wave speed had a strong positive correlation with β (r = 0.63; p < 0.001) (Figure 1C) and dP/dV (r = 0.81; p < 0.001) (Figure 1D).

Conclusions

Shear wave speed after MVC is strongly related to invasive pressure-volume loop derived measures of chamber stiffness. The results of this study indicate the potential of SWE as a novel non-invasive method for the assessment of the instantaneous stiffness of the myocardium. Abstract Figure.

On the interplay of loading, myocardial stiffness and contractility in transthoracic acoustic radiation force-induced shear wave measurements in pigs

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Research Foundation Flanders (FWO grant number 1211620N) & TTW-Dutch Heart Foundation partnership program "Early recognition of cardiovascular diseases" (project number 14740)

Background

Acoustic radiation force-based shear wave elastography (SWE) is a promising technique to non-invasively assess mechanical properties of the heart based on the propagation speed of acoustically induced shear waves. However, the interpretation of cardiac SWE measurements remains complex, and it is unclear how other factors such as loading affect shear wave propagation speed (SWS) measurements in diastole and systole.

Purpose

We applied transthoracic SWE in a pig model to investigate the dependencies of diastolic and systolic SWS on pressure-volume (PV) loop derived indices of loading, myocardial stiffness and contractility.

Methods

In 7 pigs, loading conditions were altered (increasing or decreasing preload; increasing afterload) and myocardial stiffness was changed (LAD occlusion for 60-100 minutes followed by 40 minutes of reperfusion). For each intervention, transthoracic SWE measurements were performed in a parasternal long-axis view with a high frame rate ultrasound system (> 6.2 kHz). Recordings of 28 ms were repeated at 34 Hz during 1.5 s to track shear waves throughout the cardiac cycle. To determine systolic and diastolic SWS in a robust manner, a piecewise linear model was fitted to the SWS data of each intervention representing multiple acquisitions, heartbeats and M-lines (fig. 1a). PV loops were recorded simultaneously with SWE measurements to estimate end-diastolic pressure (EDP), end-systolic pressure (ESP), end-diastolic pressure volume relation (EDPVR with exponential coefficient β in fig. 1b) and preload-recruitable stroke work (PRSW). Passive chamber stiffness was evaluated as the local slope of the EDPVR, i.e. β·EDP. Linear regressions and Pearson’s correlation coefficients were calculated.

Results

  Diastolic SWS was significantly correlated to EDP when altering loading (blue in fig. 2a: R = 0.55; p < 0.01) and stiffness (orange in fig. 2a: R = 0.66; p < 0.01). A similar correlation is found between SWS and passive chamber stiffness β·EDP (fig. 2b). Diastolic SWS is more sensitive to changes in stiffness than in loading, as reflected by the larger slope of the regression line (0.79 vs. 0.28 in fig. 2b). Furthermore, systolic SWS significantly correlated with measures of contractility during loading alterations: ESP in fig. 2c (R = 0.69; p < 0.001) and PRSW in fig. 2d (R = 0.63; p = 0.02). However, no significant correlation was found between systolic SWS and contractility during infarct/reperfusion.

Conclusion

This study shows that diastolic SWS reflects the instantaneous stiffness of the myocardium, but is not a load-independent measure of the intrinsic passive mechanical properties of the heart. Instantaneous stiffness, and thus diastolic SWS, might be altered by loading (due to material non-linearity) or intrinsic mechanical changes. Furthermore, loading experiments suggest that systolic SWS is related to contractility. The relation between SWS and contractility in the presence of myocardial infarct deserves further study. Abstract Figure. Fig. 1: SWS and PV analysis.  Abstract Figure. Fig. 2: SWS vs. PV-derived indices.

Echocardiographic assessment of mechanical dyssynchrony: are the new parameters better?

Funding Acknowledgements

Type of funding sources: None.

Introduction - The high cost and important non-response rate are preventing optimal use of cardiac resynchronization therapy (CRT). Assessing mechanical dyssynchrony on echocardiography in candidates for CRT could remove these barriers by improving patient selection. In 2008 the PROSPECT study compared several old parameters of dyssynchrony in search of a reproducible parameter capable of better predicting response to CRT. Unfortunately, the results were disappointing and the assessment of dyssynchrony became discredited. Promising new parameters have been developed but a comparison with the old parameters is currently missing.

Purpose - To compare the old and new parameters of mechanical dyssynchrony for (1) their effect on response to CRT as additional selection criteria, (2) predicting favourable long-term outcome after CRT and (3) their reproducibility.

Methods - 146 CRT patients were analysed retrospectively in a multicentre setting. Mechanical dyssynchrony was assessed using three old parameters: septal-to-posterior wall motion delay (SPWMD), left ventricular filling time/cardiac cycle ratio (LVFT/RR), and intraventricular mechanical delay (IVMD); and three new parameters: systolic stretch index (SSI), myocardial work index (MWI), and visual presence of septal flash or apical rocking (SFoAR). Response to CRT was defined as a ≥15% decrease in LV end-systolic volume 1 year after CRT. For each parameter patients were categorized using previously published cut-offs as ‘eligible’ or ‘non-eligible’. The ‘non-eligible’ were considered untreated. Results were compared to the guidelines (Fig. 1). The hazard ratio (HR) for cardiac death within 5 years after implantation was computed for all patients (Fig. 2), and intra- and interrater agreement was determined.

Results - 73% (n= 107) of patients showed response to CRT. The old parameters maintained less than 75% of the original responders. SFoAR preserved the highest proportion of responders (93%), while reducing the number of non-responders by 39% (Fig. 1). The prediction of cardiac death was significant for SFoAR (HR = 0.29; 95% CI: 0.12-0.74; P = 0.009) and IVMD (HR = 0.32; 95% CI: 0.13-0.79; P = 0.014) (Fig. 2). Intra- and interrater agreement was best for SFoAR (κ = 0.89; 95% CI: 0.67-1.0 and κ = 0.78; 95% CI: 0.50-1.0 respectively). Interrater agreement was poor for all old parameters (κ < 0.6).

Conclusion - The new parameters for dyssynchrony are performing better. The visual presence of apical rocking or septal flash provided the most responders to CRT, predicted favourable long-term outcome and was highly reproducible. Our results show that future research should focus on the new parameters. Abstract Figure.  Abstract Figure.

Left atrial mechanical dyssynchrony: an independent predictor of left ventricular reverse remodelling after cardiac resynchronization therapy

Funding Acknowledgements

Type of funding sources: Public hospital(s). Main funding source(s): Institute for Chirurgical Research - Oslo University Hospital

Introduction

Left bundle branch block (LBBB) leads to left ventricular (LV) mechanical dyssynchrony. Since the left atrium (LA) and the left ventricle (LV) are anatomically connected, dyssynchronous LV contractions may be transmitted to the LA causing LA dyssynchrony and disturbed LA function.

Purpose

To investigate if LA dyssynchrony induced by LBBB predicts LV reverse remodelling after cardiac resynchronization therapy (CRT).

Methods

In a prospective study, myocardial strain was measured by speckle-tracking echocardiography in 171 heart failure patients with LBBB, before and 6 months after CRT. LA dyssynchrony was measured as the time delay between onset systolic stretch of the interatrial septum and the LA lateral wall (white arrows in Figure), and LV dyssynchrony as the time from onset septal shortening to onset lateral wall shortening. Septal flash was assessed visually. Response to CRT was defined as at least 15 % reduction in LV end systolic volume at 6 months follow up.

Results

The figure shows a representative LBBB patient with LA and LV dyssynchrony which was abolished by CRT. For the whole study population, LA dyssynchrony was 104 ± 77 ms (mean ± SD) before CRT, and decreased to 43 ± 70 ms (p < 0.0001) after CRT. There was a significant correlation between LA and LV dyssynchrony (r = 0.68, p < 0.0001).

LA dyssynchrony correlated with LV reverse remodelling after CRT (p = 0.009), and multivariable analysis revealed that LA dyssynchrony was an independent predictor of CRT response (β=-0.046, p = 0.04) when combined with septal flash, QRS duration and QRS morphology (Table).

Conclusions

Patients with LBBB had marked LA dyssynchrony which was attributed to direct LV-LA mechanical interaction. Furthermore, LA dyssynchrony was an independent predictor of LV reverse remodelling after CRT. These findings suggest that assessment of LA dyssynchrony should be part of the echocardiographic evaluation in patients with dyssynchronous heart failure. Abstract Figure.

How well does shear wave elastography predict elevated filling pressures? a comparison to the current guideline algorithm

Funding Acknowledgements

Type of funding sources: Public hospital(s). Main funding source(s): University Hospitals (Uz) Leuven

Background

 

The assessment of left ventricular diastolic function is complex, as there is no single invasive parameter that provides a direct measurement of myocardial compliance, myocardial relaxation, or – as a surrogate - LV filling pressure. A combination of several parameters is therefore used to estimate the diastolic function.

Shear wave (SW) elastography is a novel method based on high frame rate echocardiography. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to myocardial stiffness (MS). The propagation velocity of SWs is directly related to myocardial stiffness and could be used for estimating left ventricular diastolic pressures.

Purpose

The aim of this study was to investigate if the MS at mid-diastole or end-diastole and the velocities of natural shear waves are related and, thus, could be used to estimate left ventricular end-diastolic pressures (LVEDP) as marker of diastolic function.

Methods

We prospectively enrolled 70 patients with a wide range of diastolic function, scheduled for heart catheterization so that LV mid diastolic filling pressures (LVMDP) and enddiastolic filling pressures (LVEDP) could be invasively measured (Panel B). Patients with dysfunction in the anteroseptal wall or regional myocardial abnormalities, as well as severe aortic stenosis, and a more than moderate mitral regurgitation were excluded.

Echocardiography was performed immediately after catheterization. SW elastography in parasternal long axis views of the left ventricle (LV) was performed using an experimental scanner (HD-PULSE) at 1050 ± 220 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope on the M-mode acceleration map (Panel A). Standard echocardiographic parameters of diastolic function were obtained with a high end ultrasound machine. The Algorithm for evaluating diastolic dysfunction as recommended by the European Association of Cardiovascular Imaging Guidelines 2016 was used for estimating LVMDP.

Results

SW Velocity correlated better with LVMDP (AUC = 0.8, Sensitivity = 0.84, Specificity= 0.80;  =0.26; Panels C,E) than the Guideline approach (AUC = 0.67, Sensitivity = 0.33, Specificity = 1.00, Panel G). SWV showed the best results in predicting LVEDP (AUC = 0.94, Sensitivity = 0.92, Specificity = 0.89 and =0.56 (Panels D,F)).

Conclusions

Shear wave velocities, detected by high frame rate elastography, have a strong correlation with the end-diastolic filling pressure and allowed significantly better to differentiate normal from elevated filling pressure that current guideline recommended algorithms. This suggests a potential clinical value of the new method for the non-invasive assessment of diastolic function. Abstract Figure.  Abstract Figure.

Can cardiac shear wave elastography detect the presence of septal scar in patients with left bundle branch block?

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO: Fonds Wetenschappelijk Onderzoek (fund for scientific research Flanders)

Background

Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients with left bundle branch block (LBBB). Regardless, CRT has proven to be less effective in patients with ischemic cardiomyopathy, in particular when the septum is affected. The detection of septal scar prior to CRT implantation could therefore help to improve response rate. However, magnetic resonance imaging (MRI), the gold standard to assess myocardial scar, cannot be used in every patient due to already implanted devices or impaired renal function. Cardiac shear wave elastography (SWE) allows for the non-invasive assessment of myocardial stiffness via the detection of shear waves, for example induced by mitral valve closure (MVC), that travel through the myocardium. Shear wave speed is directly related to tissue stiffness. Recently, SWE has shown to be capable to detect myocardial scar, however this has never been demonstrated in the presence of LBBB.

Purpose

To evaluate whether SWE is able to detect the presence of septal scar in patients with LBBB.

Methods

We included 34 heart failure patients with LBBB (age: 69 ± 13 y; 56% males) and with ischemic (n = 9) or non-ischemic (n = 25) cardiomyopathy and 9 age-matched healthy volunteers (age: 68 ± 4 y; 66% males) as controls. In order to obtain native ventricular conduction biventricular (BiV) pacing was turned off. All ischemic patients had septal scar only, proven by MRI or scintigraphy. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (frame rate: 932 ± 32 fps). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure A).

Results

Patient characteristics including echocardiographic parameters are shown in Table 1. Shear wave speed after MVC was significantly higher in patients with LBBB with or without septal scar compared to healthy controls (7.9 ± 1.2 m/s vs 4.5 ± 1.1 m/s; p = 0.044; 5.6 ± 1.2 m/s vs 4.5 ± 1.1 m/s: p < 0.001; figure B). This implies that the presence of LBBB alone increases myocardial stiffness. Most importantly, however, shear wave speed was significantly higher in LBBB patients with a septal scar compared to LBBB patients without a septal scar (7.9 ± 1.2 m/s vs 5.6 ± 1.2 m/s; p < 0.001; figure B), indicating that the presence of scar increases myocardial stiffness even more than LBBB alone.

Conclusions

LBBB causes a mild but significant increase in shear wave propagation speed in non-ischemic patients compared to controls. The presence of septal scarring leads to an additional and more significant increase. This indicates that SWE is capable of detecting stiffer scarred myocardium even in the presence of LBBB. Therefore, SWE could potentially be used as a novel method to detect septal scarring in LBBB patients before CRT implantation. Abstract Figure.  Abstract Figure.

Myocardial stiffness assessed by natural shear wave elastography is related to pressure-volume loop derived parameters

Background

Several cardiovascular disorders are accompanied by a stiffening of the myocardium and may result in diastolic heart failure. The non-invasive assessment of myocardial stiffness could therefore improve the understanding of the pathophysiology and guide treatment. Shear wave elastography (SWE) is a recent technique with tremendous potential for evaluating myocardial stiffness in a non-invasive way. Using high frame rate echocardiography, the propagation speed of shear waves is evaluated, which is directly related to the stiffness of the myocardium. These waves are induced by for instance mitral valve closure (MVC) and propagate throughout the cardiac muscle. However, validation of SWE against an invasive gold standard method is lacking.

Purpose

The aim of this study was to compare echocardiographic shear wave elastography against invasive pressure-volume loops, a gold standard reference method for assessing chamber stiffness.

Methods

In 15 pigs (31.2±4.1 kg) stiffness of the myocardium was acutely changed by inducing ischemia/reperfusion (I/R) injury. For this, the proximal LAD was balloon occluded for 90 minutes with subsequent reperfusion for 40 minutes. Conventional and high frame rate echocardiographic images were acquired simultaneously with pressure-volume loops during baseline conditions and after the induction of the I/R injury. Preload was reduced in order to acquire a set of pressure-volume loops to derive the end-diastolic pressure volume relation (EDPVR). From the EDPVR, the stiffness coefficient β and the operating chamber stiffness dP/dV were obtained. High frame rate echocardiographic datasets of the parasternal long axis view were acquired with an experimental ultrasound scanner (HD-PULSE) at an average frame rate of 1304±115 Hz. Tissue acceleration maps were obtained by drawing an M-mode line along the interventricular septum in order to visualize shear waves after MVC (at end-diastole). The propagation speed was assessed by semi-automatically measuring the slope (Figure A).

Results

I/R injury led to an elevated chamber stiffness constant β (0.09±0.03 1/ml vs. 0.05±0.01 1/ml; p<0.001) and operating chamber stiffness dP/dV (1.09±0.38 mmHg/ml vs. 0.50±0.18 mmHg/ml; p<0.01). Likewise, shear wave speed after MVC increased after the induction of the I/R injury in comparison to baseline (6.1±1.2 m/s vs. 3.2±0.8 m/s; p<0.001). Shear wave speed had a moderate positive correlation with β (r=0.63; p<0.001) (Figure B) and a strong positive correlation with dP/dV (r=0.81; p<0.001) (Figure C).

Conclusion

End-diastolic shear wave speed is strongly related to chamber stiffness, assessed invasively by pressure-volume loops. These results indicate that shear wave propagation speed could be used as a novel non-invasive measurement of the mechanical properties of the ventricle.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO - Research Foundation Flanders

Left bundle branch block causes left atrial dyssynchrony: a result of atrio-ventricular mechanical interaction

Introduction

Left bundle brach block (LBBB) leads to left ventricular (LV) mechanical dyssynchrony with septal flash and delayed lateral wall contractions. Since atrium and ventricle are anatomically connected, dyssynchronous LV contractions may be transmitted to the left atrium, thereby disturbing left (LA) function.

Purpose

To test the hypothesis that patients with LBBB have LA dyssynchrony induced by tethering to the dyssynchronous left ventricle.

Methods

Myocardial strain was measured by speckle-tracking echocardiography in 20 non-ischaemic heart failure patients with LBBB, before and 6 months after cardiac resynchronization therapy (CRT), and in 20 healthy controls. For the LA, dyssynchrony was measured as time delay between onset of the interatrial septum and the lateral wall, and for the LV, between onset septal flash and onset lateral wall contraction. White arrows in Figure indicate onset LA stretch.

Results

As shown in the Figure, patients with LBBB and HF had marked LA reservoir phase dyssynchrony. Before CRT time delay from onset LA septal stretch to onset lateral wall stretch was 125±71 ms (mean±SD), and decreased to 23±70 (p<0.0001) with CRT. In controls there was a small delay of 34±56 ms. The LA dyssynchrony correlated with LV dyssynchrony (r=0.50, p=0.033), supporting the hypothesis that LA dyssynchrony in LBBB represents mechanical interaction due to tethering between the respective walls.

Conclusions

Patients with LBBB had marked LA reservoir phase dyssynchrony, which was abolished with CRT. The LA dyssynchrony was attributed to direct LV-LA mechanical interaction. The observed LA resynchronization by CRT represent an additional benefit of CRT in patients with heart failure.

Funding Acknowledgement

Type of funding sources: None. Left atrial and ventricular dyssynchrony

Strain-based staging classification of left bundle branch block-induced cardiac remodeling predicts reverse remodeling after cardiac resynchronization therapy

Background

Left bundle branch block (LBBB)-induced adverse remodeling is a gradual but largely unknown process, causing a variable degree of left ventricular (LV) dysfunction and response to cardiac resynchronization therapy (CRT). In LBBB patients with septal flash (SF), an electro-mechanical continuum of different speckle-tracking strain patterns was observed, with each pattern tightly correlating with the degree of LV remodeling and dysfunction (1) (Figure 1).

Purpose

In this study, we investigated the relationship between the staged LBBB strain patterns in CRT-eligible patients and their prediction with respect to reverse remodeling and clinical outcome.

Methods

This study enrolled CRT patients from the PREDICT-CRT study population (2). Inclusion criteria were LV ejection fraction (LVEF) ≤35%, QRS duration ≥120 ms, NYHA class II–IV, absence of right ventricular pacing and availability of speckle tracking strain imaging. All patients underwent an echocardiographic examination before and 12 months after CRT implant. LV volumes, strain and dyssynchrony were assessed. Mid-septal longitudinal strain curves were classified into 5 patterns (LBBB-0 through LBBB-4; Figure 1). Primary endpoint was all-cause mortality.

Results

The study involved 250 patients (mean age 64±10 years; 79% men) with a mean LVEF of 26±7%. LBBB was present in 220 (89%) patients and 206 (82%) patients had SF. Prior to CRT implant, a LBBB-0 pattern was observed in 33 (13%), LBBB-1 in 33 (13%), LBBB-2 in 39 (16%), LBBB-3 in 44 (18%) and LBBB-4 in 101 (40%) patients. Patients with LBBB-3 and -4 patterns more frequently had LBBB, lower LVEF, increased mechanical dyssynchrony and more prominent SF (p<0.001 for all) compared with patients with LBBB-0, -1 and -2 patterns. Across the stages, CRT resulted in a gradual volumetric response, ranging from no response in stage LBBB-0 patients (ΔLV end-systolic volume +7±33%; ΔLVEF −2±9%) to super-response in stage LBBB-4 patients (ΔLV end-systolic volume −40±29%; ΔLVEF +15±13%) (p<0.001 for all). Interestingly, following reverse remodeling, the LV function of stage LBBB-2, -3 and -4 patients improved to a similar LVEF of 38% (p=1.000) in this cohort. Patients in stage LBBB-0 had a significantly less favorable five-year outcome compared to those in stage LBBB≥1 (log-rank p=0.003). There was no difference in long-term outcome between stage LBBB-1 to −4 patients (log-rank p=0.510).

Conclusion

Strain-based LBBB staging predicts the extent of LV reverse remodeling in CRT patients. CRT did not translate into improved absolute survival in the more advanced stages, but the observed gradual volumetric response suggests that CRT corrects the LBBB-induced mortality.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Sequential left ventricular electro-mechanical changes in presence of left bundle branch block

Introduction

Recent cross-sectional studies suggest a relationship between persisting left bundle branch block (LBBB) and the extent of left ventricular (LV) electro-mechanical alterations over time. When patients are referred for cardiac resynchronization therapy (CRT), temporal data during the sub-clinical phase of disease is often missing. A longitudinal study using an animal model would provide a better understanding of the relationship between the onset of LBBB and the electro-mechanical changes.

Purpose

To investigate the sequential alterations in LV structure and function that develop over time in an animal model of LBBB.

Methods

Thirteen sheep were subjected to rapid DDD pacing (180 bpm; leads on right atrium and right ventricular free wall) in order to induce a LBBB-like conduction delay. All animals underwent an 8-week pacing protocol, whereas 4 of them were subjected to 16 weeks of pacing in total. Echocardiographic speckle tracking was used to assess circumferential strain of the septal and lateral wall. Septal and lateral wall thickness were measured at end-diastole. Cardiac magnetic resonance imaging was used to determine LV volumes and ejection fraction (LVEF). Examinations took place at baseline (before and after start of pacing), and after 8 and 16 weeks of pacing. All examinations were performed at a physiologic heart rate of 110 bpm.

Results

At baseline, DDD pacing induced an increase in QRS duration (+85%, p<0.0001) and LBBB-like mechanical dyssynchrony, with mild early-systolic notching and preserved systolic shortening of the septal wall. The lateral wall demonstrated early pre-stretch followed by increasing systolic shortening. No acute changes in LV end-diastolic volume, LVEF or septal or lateral wall thickness were observed (all p>0.05). After 8 weeks of DDD pacing, mechanical dyssynchrony worsened: septal notching increased, followed by reduced systolic shortening. After 16 weeks, the initial septal shortening was followed by profound stretching throughout systole. Lateral wall systolic shortening was reduced compared to baseline. QRS duration increased further by +12% (week 8) and +20% (week 16) (all p<0.001). End-diastolic volumes had increased by +39% (week 8) and +72% (week 16), whereas LVEF had decreased by −48% (week 8) and −56% (week 16) (all p<0.001). Septal wall thickness had reduced by −24% (week 8) and −33% (week 16), while lateral wall thickness had increased by +21% (week 8) and +30% (week 16) (all p<0.05).

Conclusion

A persisting LBBB-like conduction delay induces sequential changes in LV deformation patterns, and triggers morphological and electrical remodelling. These changes are similar to those observed in patients with LBBB and different degrees of LV dysfunction. Our data suggest a continuum due to the progression of LBBB-induced LV disease. In the clinic, patients with mild dysfunction should be closely monitored in order to treat dyssynchrony as soon as guideline indications are reached.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): This work was supported by a KU Leuven research grant

Cardiac shear wave elastography can distinguish healthy and scarred myocardium in patients with conduction delays

Background

Cardiac resynchronization therapy (CRT) is an established therapy for patients suffering from heart failure and left bundle branch block (LBBB) conduction delays. Despite its proven beneficial effects, CRT is associated with a high percentage of non-response. Since CRT has shown to be less effective in patients with ischemic cardiomyopathy, determining the presence of myocardial scar before implantation could help to improve the response-rate. However, the gold standard to assess myocardial scar, magnetic resonance imaging (MRI), cannot be used in every patient, due to already implanted devices and/or reduced renal function. Recently introduced shear wave elastography (SWE) allows the non-invasive assessment of myocardial stiffness. Natural shear waves are excited by mitral valve closure (MVC) and travel through the heart with a speed directly related to tissue stiffness. SWE has previously been proven to be able to detect myocardial scar, however this has never been shown in the presence LBBB.

Purpose

The aim of this study was to evaluate the capability of SWE as a novel method to determine myocardial scar in patients with conduction delays.

Methods

We included 24 heart failure patients (age: 68±10; 50% males) with ischemic (n=8) and non-ischemic (n=16) cardiomyopathy. The CRT device was set to AAI mode in order to obtain native ventricular conduction. For patients with ischemic cardiomyopathy, the presence and location of scar was determined by MRI or scintigraphy. All ischemic patients had septal scar only. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: ±1200 Hz). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure A).

Results

There was no significant difference between the ischemic and non-ischemic patients in QRS width after CRT (149±31 ms vs 144±26 ms), systolic blood pressure blood pressure (135±11 mmHg vs 135±23 mmHg), diastolic blood pressure (74±9 mmHg vs 70±11 mmHg) and heart rate (58±4 bpm vs 63±9 bpm) (all p>0.05). Ejection fraction (33±8% vs 45±10%), end-diastolic volume (196±34 ml vs 129±64 ml) and global longitudinal strain (−9.8±3.1% vs −14.1±4.1%) differed significantly between the groups (all p<0.05). Shear wave speed after MVC was significantly higher in patients with septal scar compared to non-ischemic patients (8.2±1.9 m/s vs 5.5±1.2 m/s; p<0.01) (Figure B).

Conclusion

In the presence of scar, we found markedly elevated shear wave propagation speed compared to non-ischemic patients. These results indicate that SWE is able to identify scarred myocardium even in patients with LBBB. We therefore believe that SWE could be a novel easy and non-invasive method to evaluate septal myocardial scarring in patients before CRT implantation.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO - Research Foundation Flanders

Prognostic value of diastolic function assessment in patients undergoing cardiac resynchronization therapy

Funding Acknowledgements

Type of funding sources: None.

Objective

The best modality to assess diastolic function in CRT-candidates is an object of debate and the relationship between diastolic function, CRT-response and survival are not

clearly understood.

Purpose of the study: to assess diastolic patterns in patients undergoing CRT according to the 2016 recommendations of the American Society of Echocardiography/European Association of Cardiovascular Imaging and to evaluate the prognostic value of diastolic dysfunction (DD) in CRT candidates.

Methods

193 patients (age: 67 ± 11 years, QRS width: 167 ± 21 ms) were included in this multicentre prospective study. Patients were stratified according to DD grades (grade I

to III). CRT-response was defined as a reduction of left ventricular (LV) end-systolic volume >15% at 6-month follow-up (FU). The primary endpoint was defined as a

composite of heart transplantation, LV assisted device implantation or all-cause death during FU.

Results

During FU, 132 (68%) patients were CRT-responders. CRT delivery was associated with diastolic function degradation in non-responders. Grade I DD was able to predict

CRT-response with a sensitivity, specificity and accuracy of 70%, 65%, and 63%, respectively. After a median period of 35 months, the primary endpoint occurred in 29

(15%) patients. Grade I DD was associated with a better outcome [HR 0.26 95% CI: (0.10-0.66)], independently from ischemic cardiomyopathy, LV dyssynchrony and CRT-response (Table 1). Non-responders with grade II or grade III DD had the worse prognosis (HR 4.36, 95%CI: 2.10-9.06) Figure 1.

Conclusions

Grade I DD is associated with LV remodelling after CRT and is an independent predictor of prognosis in CRT candidates.

Abstract Figure.

Natural shear wave propagation speed is influenced by both changes in myocardial structural properties as well as loading conditions

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation - Flanders (FWO)

Background

Shear wave elastography (SWE) is a promising tool for the non-invasive assessment of myocardial stiffness. It is based on the evaluation of the propagation speed of shear waves by high frame rate echocardiography. These waves can be induced by for instance mitral valve closure (MVC) and the speed at which they travel is related to the instantaneous stiffness of the myocardium. Myocardial stiffness is defined by the local slope of the stress-strain relation and can therefore be altered by both changes in structural properties of the myocardium as well as loading conditions.

Purpose

The aim of this study was to investigate how changes in myocardial structural properties as well as loading conditions affect shear wave speed after MVC.

Methods

Until now, 8 pigs (weight: 33.6 ± 5.4 kg) were included. The following interventions were performed: 1) preload was reduced by balloon occlusion of the vena cava inferior, 2) afterload was increased by balloon occlusion of descending aorta, 3) preload was increased by intravenous administration of 500 ml of saline and 4) ischemia/reperfusion injury (I/R injury) was induced in the septal wall by balloon occlusion of the LAD for 90 min. with subsequent reperfusion for 40 min. Echocardiographic and left ventricular pressure recordings were simultaneously obtained during each intervention. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1279 ± 148 Hz). Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation speed after MVC was calculated by assessing the slope of the wave pattern on the tissue acceleration map (Figure A).

Results

The change in left ventricular end-diastolic pressure (LVEDP) and shear wave speed after MVC between baseline and each intervention are shown in Figure B and C, respectively. Preload reduction resulted in significant lower LVEDP compared to baseline (p < 0.01), while the other loading changes did not have a significant effect. Shear wave speed after MVC significantly increased by afterload and preload increase (p < 0.01). I/R injury resulted in increased shear wave speed (p < 0.01) without significantly altering LVEDP. There was a good positive correlation between the change in LVEDP and the change in shear wave speed induced by loading changes (r = 0.76; p < 0.001) (Figure D). However, the correlation became less strong if data of I/R injury was taken into account as well (r = 0.63; p < 0.001).

Conclusion

Our results suggest that SWE is capable to characterize myocardial tissue properties and besides has the potential as a novel method for the estimation of left ventricular filling pressures. However, in the presence of structural changes of the myocardium, care should be taken when estimating filling pressures based on shear wave propagation speed.

Abstract Figure.

Can shear wave imaging distinguish between diffuse interstitial and replacement myocardial fibrosis?

Funding Acknowledgements

Type of funding sources: None.

Background

  Diffuse interstitial or myocardial replacement fibrosis are common features of a large variety of cardiomyopathies. These alterations contribute to functional changes, particularly to an increased myocardial stiffness (MS). Histological examination is the gold standard for myocardial fibrosis quantification, however, it requires endomyocardial biopsy which is invasive and not without risks. Cardiac magnetic resonance (CMR) can characterize the extent of both diffuse and replacement fibrosis and may have prognostic value in various cardiomyopathies. Echocardiographic shear wave (SW) elastography is an emerging approach for measuring MS in vivo. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to MS, thus providing an opportunity to assess stiffness at end-diastole.

Purpose

The aim was to investigate if velocities of natural SW can distinguish between interstitial and replacement fibrosis. 

Methods

We prospectively enrolled 47 patients (22 patients after heart transplant [54.2 ± 15.8 years, 82.6% male] and 25 patients with established hypertrophic cardiomyopathy [54.0 ± 13.5 years, 80.0% male]) undergoing CMR during their check-up. We performed SW elastography in parasternal long axis views of the LV using a fully programmable experimental scanner (HD-PULSE) equipped with a clinical phased array transducer (Samsung Medison P2-5AC) at 1100 ± 250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope in the M-mode image. All patients underwent T1 mapping as well as late gadolinium enhancement (LGE) cardiac magnetic resonance at 1.5 T to assess the presence of diffuse or replacement fibrosis (Figure A). Therefore, patients were divided in three groups: no fibrosis, diffuse fibrosis and replacement fibrosis.

Results

Mechanical SW’s were observed in 46 subjects starting immediately after MVC and propagating from the LV base to the apex. SW propagation velocity at MVC correlated well with native myocardial T1 values (r = 0.65, p < 0.0001) and differed significantly among groups (p < 0.0001), with a significant post-test between any pair of groups (Figure B). SW velocities below a cut-off of 6.01 m/s showed the highest accuracy to identify patients without any type of fibrosis (sensitivity 88 %, specificity 89%, area under the curve = 0.93) (Figure C). A cut-off of 8.11 m/s could distinguish replacement fibrosis from diffuse fibrosis with a sensitivity and specificity of 59% and 92 %, respectively (area under the curve = 0.80) (Figure D).

Conclusions

  Shear wave velocities after mitral valve closure can distinguish between normal and pathological myocardium and can detect differences between diffuse and replacement fibrosis.

Abstract Figure.

Closed-chest measurement of diastolic and systolic shear wave speed to assess myocardial stiffness

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Research Foundation Flanders (FWO): grant 1211620N TTW – Dutch Heart Foundation partnership program "Earlier recognition of cardiovascular diseases": project number 14740

Background

Echocardiographic shear wave elastography (SWE) encompasses all ultrasound techniques tracking shear wave (SW) motion in the cardiac wall, of which the propagation speed is linked to the intrinsic mechanical properties. SWs can be induced naturally, for example by valve closure, or externally by using an acoustic radiation force (ARF). Although the latter is technically more demanding, it enables instantaneous stiffness assessment throughout the entire cardiac cycle (fig. a). However, it is unknown how factors such as cardiac loading and contractility, next to intrinsic mechanical properties, affect ARF-based SW speeds.

Purpose

We performed transthoracic SWE measurements in pigs to study the effects of hemodynamic alterations, inotropic state and myocardial infarction (MI) on diastolic and systolic SW speeds.

Methods

Different cardiac conditions were considered in three pigs: (i) baseline (BL), (ii) preload decrease (PD), (iii) afterload increase (AI), (iv) preload increase (PI), (v) administration of dobutamine (DOB), (vi) BL2, (vii) MI through 60-100 min. occlusion of the LAD and (viii) 40 min. reperfusion (REP). For each condition, transthoracic high frame rate ARF-based SWE acquisitions were taken in a parasternal long-axis view with a research ultrasound system. SWs were induced in the septum at 34 Hz during 1.5 s to track SW speeds throughout the cardiac cycle (fig. a&b). Systolic and diastolic SW speeds were determined from the 10% highest and lowest median values per condition, respectively. Left ventricular pressure-volume (PV) loops were recorded to estimate end-diastolic pressure (EDP), end-systolic pressure (ESP) and passive chamber stiffness (dPdV). dPdV was determined as the slope of the tangent to the fitted end-diastolic PV relationship at mean ED volume. Linear regressions and Pearson’s correlation coefficients were computed.

Results

Diastolic SW speed was correlated to EDP for conditions with changes in loading, and to dPdV for conditions with changes in chamber stiffness (fig. c).  Both relationships were significant, with a moderate positive correlation for EDP (R = 0.48, p = 0.02) and a strong positive correlation for dPdV (R = 0.76, p < 0.01). Furthermore, the observed change in diastolic SW speed was smaller when altering EDP compared to dPdV (0.4 m/s vs. 1.0 m/s). For systolic SW speed, very strong positive correlations were found with ESP (R = 0.91, p < 0.01), and with dPdV (R = 0.81, p < 0.01) in fig. d.

Conclusion

This study shows that both diastolic and systolic SW speed are related to passive chamber stiffness. Moreover, loading also influenced systolic SW speed and, to a lesser extent, diastolic SW speed, presumably because of material nonlinearity. Systolic SW speed is linked to contractility as well. Thus, while SWs after valve closure occur at a certain moment in the cardiac cycle, the timing of ARF-based SWs can be chosen such to assess specific aspects of the cardiac (structural and functional) status.

Abstract Figure.

Localizing myocardial scar on echocardiography. How good does it work in the presence of conduction delays?

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation - Flanders (FWO)

Introduction

Myocardial scar detection with echocardiography in patients with ischemic heart disease typically relies on semi-quantitative evaluation of regional systolic wall thickening. In patients scheduled for cardiac resynchronization therapy (CRT) however, such echo scar estimation is complicated by the presence of dyssynchronous contraction and differential regional remodelling. Visual assessment of myocardial shortening during systole may be an alternative approach. We tested this against cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE) in patients without and with conduction delay.

Methods

122 patients with ischemic heart disease were included (n = 58 without, and n = 64 with conduction delay). Scar burden of the LV was determined in all patients on a segmental level in both CMR and echo. Reading of echo was blinded for CMR data and vice versa. Myocardial scar was defined as LGE > 50% of transmural thickness. On echo, scar was assessed visually, and defined as thin, echogenic myocardium with no visible shortening during systole. Analysis was performed per segment (18 segment model), and per region (6 walls with basal and mid segment and the apex region consisting of all apical segments). An additional analysis was performed with a tolerance of one adjacent segment in order to account for potential image misalignment between modalities.

Results

2196 segments were available for comparison between echo and CMR. On CMR, 548 of those segments were defined as having >50% transmural scar. In echo, 565 segments were detected as having scar. On a segmental level, no difference was found for the correct assignment of segments by echo as having scar or not between patients without or with conduction delay (AUC 0.79 vs. 0.79; p = 0.968) (Figure, top panels). See Figure for sensitivity and specificity. If one segment tolerance was allowed, segments were correctly assigned with equal accuracy in both patient groups (AUC 0.98 vs. 0.96; p = 0.999) (see Figure; w. tolerance). Agreement on the level of LV regions was comparable. 295 regions had a scar on CMR while 286 regions were identified by echo. Echo correctly identified a scar in the same LV wall or apex as compared to CMR similarly in patients without or with conduction delay (AUC 0.79 vs. 0.77; p = 0.698). If one segment tolerance was allowed, correct identification improved further and was not different between both groups (AUC 0.93 vs. 0.91; p = 0.999). The extent of a scar was slightly underestimated (9%) by echocardiography in comparison to CMR in patients without, and slightly overestimated (3%) in patients with conduction delays.

Conclusions

Scars can be localized on echocardiography with good agreement to CMR-LGE as gold standard. The match between echo and CMR was similar for patients with and without conduction delay. Our findings demonstrate that echo can provide a valid impression of localization and extent of myocardial scar, even in the presence of conduction delays.

Abstract Figure.

Shear wave elastography: can we discover elevated diastolic filling pressures?

Funding Acknowledgements

Type of funding sources: Public hospital(s). Main funding source(s): University Hospitals (Uz) Leuven

Background

 The assessment of the left ventricular diastolic function is complex, as there is no single invasive parameter that provides a direct measurement of myocardial relaxation, myocardial compliance, or – as a surrogate - LV filling pressure. Estimation of diastolic function is therefore based on the combination of several parameters.

Shear wave (SW) elastography is a novel method based on high frame rate echocardiography. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to myocardial stiffness (MS).

Purpose

The aim of this study was to investigate if velocities of natural shear waves are related to MS at end-diastole (ED) and, thus, could be used to estimate left ventricular end-diastolic pressures (LVEDP) as marker of diastolic function.

Methods

So far, we have prospectively enrolled 42 patients with a wide range of diastolic function, scheduled for heart catheterization so that LV filling pressures could be invasively measured. Patients with severe aortic stenosis, mitral stenosis of any degree and a more than moderate mitral regurgitation, as well as regional myocardial abnormalities or dysfunction in the anteroseptal wall were excluded.

Echocardiography was performed immediately after catheterization. SW elastography in parasternal long axis views of the left ventricle (LV) was performed using an experimental scanner (HD-PULSE) at 1100 ± 250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope on the M-mode acceleration map (Figure A). Standard echocardiographic parameters of diastolic function were obtained with a high end ultrasound machine.

Results

SW velocities at ED correlated well with the invasively measured LVEDP (r = 0.74, p < 0.001, Figure B). In comparison, classical echocardiographic parameters correlated only weakly with LVEDP (E/A: r = 0.398, p = 0.02, Figure C; E/E’: r = 0.204, p = 0.247, Figure D).

For the detection of an elevated LVEDP above 15 mmHg, a cut off value for the SW velocity at MVC of 4.395 m/s (Figure A) was associated with a sensitivity of 91.3% and a specificity of 90.9%.

Conclusions

End-diastolic shear wave velocities, measured by high frame rate shear wave elastography, showed a significant correlation with the end-diastolic filling pressure of the LV and allowed to differentiate normal from elevated filling pressure which indicates a potential clinical value of the new method for a non-invasive and direct assessment of LV diastolic function. More patients will be included to confirm these findings.

Abstract Figure.

Relationship between myocardial properties and myocardial stiffness in hearts with thick walls: a shear wave imaging study using ultra-high frame rate echocardiography

Funding Acknowledgements

Type of funding sources: None.

Background

Shear wave (SW) imaging, based on high frame rate (HFR) echocardiography, is a new non-invasive approach for assessing myocardial stiffness. Operating myocardial stiffness increases with increasing wall stress, therefore measured myocardial stiffness does not necessarily reflect intrinsic myocardial properties only, but can be influenced by cavity pressure and chamber geometry.

Purpose

 To explore the relationship between local myocardial geometry, cavity pressure and pathological substrate with SW velocity and to determine to which extent the above mentioned factors influence SW velocity.

Methods

We included 26 healthy controls (55 ± 14 years, 77 % male) and 61 patients with thick heart (24 patients with cardiac amyloidosis (AML) [70 ± 9 years, 52 % male], 37 patients with hypertrophic cardiomyopathy (HCM) [54 ± 14 years, 78 % male]). Left ventricular (LV) parasternal long axis views were acquired with an experimental HFR scanner at 1142 ± 282 frames per seconds. Propagation velocity of the SW occurring after mitral valve closure in the interventricular septum (IVS) served as measure of myocardial stiffness (Figure A). While conventional echocardiographic measurements were used to evaluate local myocardial geometry (LV end-diastolic diameter [EDD], IVS thickness) and LV cavity pressure (LV diastolic pressure-estimated by E/e` and LV systolic pressure-estimated by systolic blood pressure and potential LV outflow gradient in HCM).

Results

 LV cavity pressure and local geometry differed significantly between controls and patients (p < 0.05, for all, Figure B). SW velocity correlated with cavity pressure (E/e`: r = 0.375, p < 0.001, LV systolic pressure: r = 0.264, p = 0.020) and local geometry (IVS thickness: r = 0.700, p < 0.001; EDD: r=-0.307, p = 0.007) and differed significantly among groups (Figure C). Multivariate analysis revealed that SW velocity was independently related only with the pathological substrate and IVS thickness (p = 0.006 and p < 0.001, respectively). In a regression model, the pathological substrate, cavity pressure and local geometry accounted for 56% of variation in SW velocity (p < 0.001), while the pathological substrate alone accounted for nearly half of the variance (R2 = 0.44, p < 0.001) (Figure D).

Conclusions

 Our study demonstrated that SW velocity is related to both pathological substrate and local geometry and LV pressures. Additionally, our results suggest that variations in myocardial tissue properties had the most influence on SW velocity, while LV pressure and local geometry played a minor role. Therefore, the changes in SW velocity reflect predominantly tissue properties that are altered by underlining disease rather than cavity pressure and morphological abnormalities. Thus, SW elastography could provide useful novel diagnostic information in the evaluation of cardiomyopathies.

Abstract Figure A, B, C, D

Vendor-independent software shows limited variability in speckle tracking strain measurements on images of different vendors

Funding Acknowledgements

Type of funding sources: None.

Background

Vendors use proprietary speckle tracking software algorithms for echocardiographic strain measurements, which results in high inter-vendor variability. Little is known about potential advantages or disadvantages of using vendor-independent software in clinical practice.

Purpose

We therefore investigated the reproducibility, accuracy, and ability to identify scar of strain measurements on images from different vendors by using a vendor-independent software.

Methods

A vendor-independent software (TomTec Image Arena) was used to analyze datasets of 63 patients which were obtained on four ultrasound machines from different vendors (GE, Philips, Siemens, Toshiba). We measured the tracking feasibility, inter-vendor bias, the relative and absolute test-re-test variability of strain measurements and their ability to detect scar. Cardiac magnetic resonance delayed enhancement images were used as the reference standard of scar definition.

Results

Tracking feasibility differed depending on the image source (p < 0.05). Variability of global longitudinal strain (GLS) (Figure 1A) was similar (ANOVA p = 0.124) among the images of different vendors whereas variability of segmental longitudinal strain (SLS) (Figure 1B) showed modest difference (ANOVA- peak systolic strain (PS); p = 0.077, end-systolic strain (ES); p = 0.171, post-systolic strain (PSS); p = 0.020). Relative test-re-test variability of GLS showed no differences (ANOVA p = 0.360). Absolute test-re-test errors of SLS measurements showed modest differences among images of different vendors (ANOVA- PS; p = 0.018, ES; p = 0.001, PSS; p = 0.090). No relevant difference in scar detection capability was observed (Figure 1C).

Conclusions

Vendor independent software leads to low bias among strain measurements on images from different vendors. Likewise, measurement variability and the ability to identify scar becomes similar. Our findings suggest that a vendor independent speckle tracking software could help to overcome inter-vendor bias. To which extend such measurements would be more accurate compared to vendor specific software remains to be determined.

Abstract Figure 1

Importance of systematic right ventricular assessment in cardiac resynchronization therapy candidates: a machine-learning approach

Funding Acknowledgements

Type of funding sources: None.

Background

Despite having all a systolic heart failure and broad QRS, patients proposed for cardiac resynchronization therapy (CRT) are highly heterogeneous and it remains extremely complicated to predict the impact of the device on left ventricular (LV) function and outcomes.

Objectives

We sought to evaluate the relative impact of clinical, electrocardiographic, and echocardiographic data on the left ventricular (LV) remodeling and prognosis of CRT-candidates by the application of machine learning (ML) approaches.

Methods

193 patients with systolic heart failure undergoing CRT according to current recommendations were prospectively included in this multicentre study. We used a combination of the Boruta algorithm and random forest methods to identify features predicting both CRT volumetric response and prognosis (Figure 1). The model performance was tested by the area under the receiver operating curve (AUC). We also applied the K-medoid method to identify clusters of phenotypically-similar patients.

Results

From 28 clinical, electrocardiographic, and echocardiographic-derived variables, 16 features were predictive of CRT-response; 11 features were predictive of prognosis.

Among the predictors of CRT-response, 7 variables (44%) pertained to right ventricular (RV) size or function. Tricuspid annular plane systolic excursion was the main feature associated with prognosis. The selected features were associated with a very good prediction of both CRT response (AUC 0.81, 95% CI: 0.74-0.87) and outcomes (AUC 0.84, 95% CI: 0.75-0.93) (Figure 1, Supervised Machine Learning Panel). An unsupervised ML approach allowed the identifications of two phenogroups of patients who differed significantly in clinical and parameters, biventricular size and RV function. The two phenogroups had significant different prognosis (HR 4.70, 95% CI: 2.1-10.0, p < 0.0001; log –rank p < 0.0001; Figure 1, Unsupervised Machine Learning Panel).

Conclusions

Machine learning can reliably identify clinical and echocardiographic features associated with CRT-response and prognosis. The evaluation of both RV-size and function parameters has pivotal importance for the risk stratification of CRT-candidates and should be systematically assessed in patients undergoing CRT.

Abstract Figure 1

Regional myocardial work as determinant of heart failure in left bundle branch block

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): The Norwegian Health Association

Background

Left bundle branch block (LBBB) worsen prognosis in heart failure patients. LBBB may also cause heart failure in otherwise healthy individuals. The mechanical changes induced by LBBB are potential determinants of heart failure in these patients, but their relation to left ventricular (LV) systolic function is incompletely understood.

Purpose

This study investigates the contribution of regional contractile function to heart failure in patients with LBBB.

Methods

In 76 patients with LBBB and 11 healthy controls, myocardial strain was measured by speckle-tracking echocardiography and myocardial work by pressure-strain analysis. Patients with ischemic heart disease or myocardial scarring were excluded. LBBB patients were stratified by LV ejection fraction (EF) >50% (EFpreserved), 36-50% (EFmid), and ≤35% (EFlow). 62 LBBB patients subsequently underwent cardiac resynchronization therapy (CRT) implantation and was re-examined at 6 months.

Results

Septal work was significantly and successively reduced from controls, EFpreserved, EFmid, to EFlow (1977 ± 506, 1025 ± 342, 601 ± 494 and -41 ± 303 mmHg·%, respectively, all p < 0.01) (Figure 1). There was a strong correlation (R = 0.84, p < 0.01) between septal work and LVEF. In contrast, work in the LV lateral wall was preserved in both EFpreserved (2367 ± 459 mmHg·%) and EFmid (2252 ± 449 mmHg·%) vs controls (2062 ± 459 mmHg·%, all NS). In the EFlow group, however, LV lateral wall work was reduced (1473 ± 568 mmHg·%, p < 0.01 vs controls). Thus, lateral wall function was not correlated with LVEF in patients with LVEF >35% (NS). At six month CRT septal work was markedly increased (165 ± 485 vs 1288 ± 523 mmHg·%, p < 0.01) and LV lateral wall work reduced (1730 ± 620 vs 1264 ± 490 mmHg·%, p < 0.01). LVEF increased from 32 ± 8 to 47 ± 10 % (p < 0.01).

Conclusions

Heart failure in LBBB patients is determined by degree of septal dysfunction. LV lateral wall function, on the other hand, is preserved in the early phase of heart failure and was only reduced in patients with severe heart failure. Further clinical studies should investigate if measuring LV lateral wall function can increase precision in patient selection for CRT.

Abstract Figure.

The influence of hemodialysis-induced preload changes on the propagation speed of natural shear waves

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation - Flanders (FWO)

Background

Shear wave elastography (SWE) is a novel ultrasound technique based on the detection of transverse waves travelling through the myocardium using high frame rate echocardiography. The propagation speed of these shear waves is dependent on the stiffness of the myocardium. Previous studies have shown the potential of SWE for the non-invasive assessment of myocardial stiffness. It is unclear, however, if preload changes lead to measurable changes in the shear wave propagation speed in the left ventricle. In patients undergoing hemodialysis, the volume status is acutely changed. In this way, the effect of preload changes on shear wave speed can be assessed.

Purpose

The aim of this study was to explore the influence of preload changes on end-diastolic shear wave propagation speed.

Methods

Until now, 6 patients (age: 80[53-85] years; female: n = 2) receiving hemodialysis treatment were included. Echocardiographic images were taken before and every hour during a 4 hour hemodialysis session. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1016[941-1310] Hz). Standard echocardiography was performed with a conventional ultrasound machine. Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation speed after mitral valve closure (MVC) was calculated by measuring the slope of the wave pattern on the acceleration maps (Figure A).

Results

Over the course of hemodialysis, the systolic (141[135-156] mmHg vs. 165[105-176] mmHg; p = 0.35 among groups) and diastolic blood pressure (70[66-75] mmHg vs. 82[63-84] mmHg; p = 0.21 among groups), heart rate (56[54-73] bmp vs. 57[50-67] bpm; p = 0.76 among groups), E/A ratio (1.6[0.7-1.8] vs. 1.2[0.6-1.4]; p = 0.43 among groups) and E/e’ (14[9-15] vs. 9[8-13]; p = 0.24 among groups ) remained the same. The ultra-filtrated volumes are shown in Figure B. The shear wave propagation speed after MVC gradually decreased during hemodialysis (6.7[5.4-9.7] m/s vs. 4.4[3.6-9.0] m/s; p = 0.04 among groups) (Figure C). There was a moderate negative correlation between shear wave speed and the ultra-filtrated volume (r=-0.63; p < 0.01) (Figure D).

Conclusion

The shear wave propagation speed at MVC significantly decreased over the course of hemodialysis and correlated to the ultra-filtrated volume. These results indicate that alterations in left ventricular preload affect the speed of shear waves at end-diastole. End-diastolic shear wave speed might therefore be a potential novel parameter for the evaluation of the left ventricular filling state. More patients will be included in the future to further explore these findings.

Abstract Figure.

Elevated septal wall stress - a driver of left ventricular dysfunction in left bundle branch block?

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): The Norwegian Health Association

Background

Septal dysfunction is a main feature of left bundle branch block (LBBB), and increasing wall stress is a proposed mechanism of heart failure development in LBBB patients. To try to reveal the pathophysiologic pathway from dyssynchrony to heart failure, we investigated the relationship between septal and left ventricular (LV) lateral wall stress in patients with LBBB.

Hypothesis

Increased septal wall stress causes septal dysfunction in LBBB.

Methods

We included 24 LBBB-patients (65 ± 11 years, 11 males) with LV ejection fraction (EF) ranging from 18 to 67%, and 8 healthy controls (58 ± 10 years, 4 males). Wall stress was calculated at peak LV pressure (LVP) according to the law of La Place ([LVP x radius]/[wall thickness]). Wall thickness was measured using M-mode, and regional curvature was measured in mid-ventricular shortaxis from 2D echocardiographic images. We used a previously validated non-invasive method to estimate LVP from brachial blood pressure and adjusted for valvular events. Myocardial scar was ruled out by late gadolinium enhancement cardiac magnetic resonance imaging.

Results

Wall stress was significantly higher in septum than LV lateral wall at peak LVP (48 ± 12 vs 37 ± 11 kPa, p < 0.01) in LBBB patients, while no difference was seen in the controls (Figure A). In patients, septal wall thickening showed a strong correlation with LVEF (r = 0.77, p < 0.01) (Figure B). Similar correlation was not significant for the LV lateral wall (r = 0.13, NS). Attenuation of septal wall thickening in LBBB-patients correlated well with increasing septal wall stress (r=-0.60, p < 0.01). Wall thickening and stress did not correlate in the LV lateral wall (r=-0.14, NS).

Conclusion

Increased septal wall stress is associated with reduced systolic thickening in patients with LBBB. Septal wall thickening, in contrast to LV lateral wall thickening, was correlated to global LV function. These findings suggest that septal remodeling which could have normalized septal wall stress, was not achieved and heart failure may develop.

Abstract Figure.

Septal scar predicts non-response to cardiac resynchronization therapy

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): South-Eastern Norway Regional Health Authority Norwegian Health Association

Background

Scar in the left ventricular (LV) posterolateral wall is associated with poor response to cardiac resynchronization therapy (CRT). The impact of septal scar, however, has been less thoroughly investigated. As recovery of septal function seems to be an important effect of CRT, we hypothesized that CRT response depends on septal viability.

Aim

The aim of the present study was to investigate the association between septal scar and volumetric response to CRT, and to compare the impact of scar located in septum to scar located in the posterolateral wall.

Methods

128 patients with symptomatic heart failure undergoing CRT implantation based on current guidelines (ejection fraction 30 ± 8%, QRS-width 164 ± 17 ms) were included in the study. Volumes and ejection fraction were measured by echocardiography using the biplane Simpson’s method at baseline and six months follow up. Non-response was defined as less than 15% reduction in end-systolic volume. Scar was assessed by late gadolinium enhancement cardiac magnetic resonance, and reported as percentage scar per regional myocardial volume. Numbers are given in [median ;10-90% percentile].

Results

Scar was present in 62 patients (48%). Scar burden was equal in septum [0% ;0-34%] and the posterolateral wall [0% ;0-36%], p = 0.10. 31 patients (24%) did not respond to CRT. The non-responders had higher scar burden than the responders in both septum [16% ;0-57% vs 0% ;0-23%, p < 0.001] and the posterolateral wall [6% ;0-74% vs 0% ;0-22%, p < 0.001].

In univariate regression analysis both septal and posterolateral scars correlated with non-response to CRT (r = 0.51 and r = 0.33, respectively). However, combined in a multivariate model only septal scar remained a significant marker of non-response (p < 0.001), while posterolateral scar did not (p = 0.23).

Septal scar ≥ 7.1% predicted non-response with a specificity of 81% and a sensitivity of 70% by receiver operating characteristic curve analyses. The area under the curve was 0.79 (95% confidence interval 0.70 – 0.89) (Figure).

Conclusions

Septal scar is more closely associated with volumetric non-response to CRT than posterolateral scar. Future studies should explore the correlation between regional scar burden and different functional parameters, and how they relate to CRT response.

Abstract Figure. Septal scar predicts non-response to CRT

Prognostic utility of the assessment of diastolic function in patients undergoing cardiac resynchronization therapy

Conflicting data exist about the relationship between cardiac resynchronization therapy (CRT) and diastolic function. Aims of the study are to assess diastolic patterns in patients undergoing CRT according to the 2016 recommendations of the American Society of Echocardiography/European Association of Cardiovascular Imaging and to evaluate the prognostic value of diastolic dysfunction (DD) in CRT candidates. METHODS AND RESULTS: One-hundred ninety-three patients (age: 67 ± 11 years, QRS width: 167 ± 21 ms) were included in this multicentre prospective study. Mitral filling pattern, mitral tissue Doppler velocity, tricuspid regurgitation velocity, and indexed left atrial volume were used to classify DD from grade I to III. CRT-response, defined as a reduction of left ventricular (LV) end-systolic volume > 15% at 6-month follow-up (FU), occurred in 132 (68%) patients. The primary endpoint was a composite of heart transplantation, LV assisted device implantation, or all-cause death during FU and occurred in 29 (15%) patients. CRT was associated with a degradation of DD in non-responders. At multivariable analysis corrected for clinical variables, QRS duration, mitral regurgitation, CRT-response and LV dyssynchrony, grade I DD was associated with a better outcome (HR 0.37, 95% CI: 0.14-0.96). Non-responders with grade II-III DD had the worse prognosis (HR 4.36, 95%CI: 2.10-9.06). CONCLUSIONS: The evaluation of DD in CRT candidates allows the prognostic stratification of patients, independently from CRT-response.

Echocardiographic assessment of CRT candidates. Does it work equally well in intermediate QRS duration?

Background

The presence of mechanical dyssynchrony – such as apical rocking (ApRock) and septal flash (SF) – on echocardiography is associated with favourable outcome after cardiac resynchronization therapy (CRT). Myocardial scar on the other hand, has a considerable negative impact on CRT response. There is growing evidence that a visual echocardiographic assessment of mechanical dyssynchrony by ApRock, SF and scar predicts CRT response. Little is known however if this works equally well in patients with intermediate QRS duration (120–150ms), where guideline recommendation for CRT is weaker.

Methods

A total of 400 unselected patients referred for CRT, who fulfil the contemporary guidelines, were enrolled in this multicentre study. Echocardiographic images were visually assessed before CRT implantation, focussing on the presence of ApRock, SF and location and extent of scar segments in the left ventricle (LV), resulting in a CRT response prediction (i.e. Reader Interpretation). Readers were blinded to all patient information other than ischaemic aetiology of heart failure. CRT response was defined as ≥15% reduction in LV end-systolic volume on echocardiography, on average 15 months after device implantation.

Results

Overall, 321 (80%) patients had a left bundle branch block (LBBB), with an average QRS duration of 166±25ms. Ischemic aetiology of heart failure was found in 131 (33%) patients. Before CRT, ApRock and SF were present in 254 (64%) and 244 (61%) patients, respectively. ApRock and SF alone predicted CRT response with an area under the curve (AUC) of 0.79 (95% CI: 0.74–0.84) and 0.78 (95% CI: 0.73–0.83) (Figure A), while the echocardiographic Reader Interpretation had an AUC of 0.85 (95% CI: 0.81–0.89), with a sensitivity of 89% and a specificity of 82% for the prediction of CRT response (Figure B) (p<0.0001 vs. ApRock and SF alone). A total of 92 patients had a QRS duration of 120–150ms, and 48 of them responded to CRT. In these patients, the AUC of Reader Interpretation was comparable to that of the entire study cohort [0.83 (95% CI: 0.75–0.92)], as was sensitivity and specificity (90% and 79%, respectively, p=0.717 vs. the AUC of the entire cohort) (Figure C).

Conclusions

A visual assessment of LV function, by means of mechanical dyssynchrony and scar, has an excellent predictive value for CRT response, and requires only apical echocardiographic images. Responders were identified equally well in the challenging subgroup of patients with a QRS duration of 120–150 ms.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): KU Leuven

Shear wave elastography by high frame rate echocardiography can detect diffuse myocardial fibrosis after heart transplantation

Background

Myocardial fibrosis is fundamental in the development of cardiac failure, regardless of ethiology. In both animal models and humans it has been shown that diffuse myocardial fibrosis (DMF) contributes to functional impairment, especially to increased passive myocardial stiffness, which is an important pathophysiological determinant of left ventricular diastolic dysfunction. Histological examination is the gold standard for myocardial fibrosis quantification, however, it requires endomyocardial biopsies which are invasive and not without risk. Echocardiographic shear wave (SW) elastography, based on high frame rate imaging, is an emerging approach for measuring myocardial stiffness in vivo. Natural SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC) and their propagation velocity is directly related to myocardial stiffness, thus providing an opportunity to assess myocardial stiffness at end-diastole.

Purpose

The aim was to investigate if propagation velocities of natural SWs can be used to detect diffuse myocardial fibrosis in a cohort of heart transplant recipients.

Methods

We prospectively enrolled 22 patients (10.3±6.3 years after HTx) that underwent CMR during their annual check-up. We performed SW elastography in parasternal long axis views of the left ventricle using a fully programmable experimental scanner (HD-PULSE) equipped with a clinical phased array transducer (Samsung Medison P2–5AC) at 1100±250 frames per second. The SW propagation velocities at MVC were measured in the basal LV septum. Native T1 and extracellular volume (ECV) were measured at the same segment to evaluate DMF. A cut-off value for native T1 of 1040 ms and for ECV of 29% was used to define DMF in our cohort.

Results

We found good correlations between SW velocities and both myocardial T1 (r=0.80, p<0.0001, Figure A) and ECV (r=0.64, p=0.003, Figure B) measured with CMR. Further, we derived reference thresholds of natural SW velocities to identify DMF in HTx patients. The optimal cut-off value of SW velocity to identify patients with nativT1>1040 ms was 4.84 m/s (AUC 0.81, sensitivity 82%, specificity 82%, Figure C). To identify patients with ECV>0.29 the cut-off value of SW velocity was 4.74 m/s (AUC 0.74, sensitivity 73%, specificity 78%, Figure D).

Conclusions

End-diastolic shear wave propagation velocities, as measure of myocardial stiffness, showed a good correlation with CMR defined diffuse myocardial injury. Values higher than 4.74 m/s could identify diffuse myocardial injury in HTX patients with a good sensitivity and good specificity. These findings thus suggest that shear wave elastography has the potential to become a valuable non-invasive method for the detection of diffuse myocardial fibrosis.

Funding Acknowledgement

Type of funding source: None

Better diastolic function in CRT candidates is associated with improved survival after CRT implantation

Background

The relationship between diastolic dysfunction (DD) and outcome after CRT is debated.

Purpose

Purpose of this study was to evaluate the role of DD in predicting all-cause mortality in heart failure patients undergoing CRT.

Methods

One-hundred ninety-three patients (age: 67±11 years, QRS width: 167±21 ms, LVEF 28±8%) were included in this multicentre prospective study. Mitral filling pattern, mitral tissue Doppler velocity, tricuspid regurgitation velocity, and indexed left atrial volume were used to classify DD from grade I to III according to the 2016 recommendations of the American Society of Echocardiography/European Association of Cardiovascular Imaging. A reduction of LV end-systolic volume >15% at 6-month follow-up (FU) identified CRT-responders and was observed in 132 (68%) patients.

Results

During a median 35 months FU, 29 (15%) patients died. Through multivariable analysis, coronary artery disease, NYHA functional class and grade I DD were shown to be independent predictors of prognosis (Table 1). Grade I DD was associated with a longer survival rate in both responders and non responders (Figure 1). Non responders with grade II-III DD had the worse outcome (HR 12.5 [3.56–44.04], p<0.0001).

Conclusions

Better diastolic function at baseline is associated with an improved survival after CRT implantation, independently of CRT-response.

Funding Acknowledgement

Type of funding source: None

The behaviour of natural shear waves under different loading conditions

Background

Shear wave imaging (SWI) is a novel ultrasound technique based on the detection of transverse waves traveling through the myocardium using high frame rate echocardiography. These waves can be naturally induced e.g. by mitral valve closure (MVC). Their propagation velocity is dependent on the stiffness of the myocardium. Previous studies have shown the potential of SWI for the non-invasive assessment of myocardial stiffness. So far, the influence of loading on shear wave propagation velocities has not been extensively investigated.

Purpose

The aim of this study was to explore how loading changes affect shear wave propagation velocities after MVC.

Methods

Until now, 5 pigs (weight: 33.5±6.9 kg) were included. Echocardiographic images and left ventricular pressure recordings were simultaneously acquired during acute loading alterations: 1) preload was reduced by balloon occlusion of the vena cava inferior, 2) afterload was increased by balloon occlusion of the descending aorta and 3) preload was increased by intra-venous administration of 500 ml of saline. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1247±179 Hz). Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation velocities after MVC were calculated by measuring the slope of the wave front on the acceleration maps (Figure A).

Results

The changes in left ventricular end-diastolic pressures (LV EDP) between baseline and each intervention are shown in Figure B. Preload reduction resulted in significantly reduced LV EDP (p<0.01). The shear wave propagation velocities after MVC dropped with preload reduction and increased significantly by increasing afterload as well as preload (both p<0.05) (Figure C). There was a good positive correlation between the change in LV EDP and the change in shear wave velocities (r=0.83; p<0.001) (Figure D).

Conclusion

The shear wave propagation velocity after MVC was significantly influenced by alterations in left ventricular loading conditions and changes in these velocities were related to changes in LV EDP. These results indicate that shear wave measurements at MVC might be a potential novel parameter for the estimation of left ventricular filling pressures. More pigs will be included in the future to further confirm these findings.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek - Vlaanderen

Differentiation of hypertensive heart disease and hypertrophic cardiomyopathy with myocardial stiffness measurements: a shear wave imaging study using ultra-high frame rate echocardiography

Background

Recently, cardiac shear wave (SW) elastography, based on high frame rate (HFR) echocardiography, has been proposed as new non-invasive technique for assessing myocardial stiffness. As myocardial stiffness increases with increasing wall stress, differences in measured operating myocardial stiffness do not necessarily reflect differences in intrinsic myocardial properties, but can also be caused by mere changes in loading or chamber geometry. This complicates myocardial stiffness interpretation for different types of pathologic hypertrophy.

Purpose

To explore the relationship between myocardial stiffness and underlying pathological substrates for cardiac hypertrophy.

Methods

We included 20 patients with hypertension (HT) and myocardial remodelling (59±14 years, 75% male), 20 patients with hypertrophic cardiomyopathy (HCM) (59±16 years, 60% male) and 20 healthy controls (56±14 years, 75% male). Left ventricular (LV) parasternal long axis views were acquired with an experimental HFR scanner at 1293±362 frames per seconds. Propagation velocity of SW occurring after mitral valve closure in the interventricular septum (IVS) served as measure of operating myocardial stiffness (Figure A). To compare myocardial stiffness among hearts with differing loading conditions and chamber geometry, SW velocities were normalized to end-diastolic wall stress, estimated at IVS from regional wall thickness, longitudinal and circumferential regional radii of curvature, and non-invasively estimated LV end-diastolic pressure (EDP).

Results

SW velocities differed significantly between groups (p<0.001). The controls had the lowest SW velocities (4.02±0.97 m/s), whereas values between HT and HCM group were comparable (6.46±0.99 m/s vs. 7.00±2.10 m/s; p=0.738). Considering end-diastolic wall stress, HCM patients had the same SW velocity at lower wall stress compared to HT (Figure B), indicating higher myocardial stiffness in the HCM group. SW velocities normalized for wall stress indicated significantly different myocardial stiffness among all groups (p<0.001) (Figure C). In a multiple linear regression model, the underlying pathological substrate independently influenced SW velocity (beta 1.37, 95% CI (0.78–1.96); p<0.001), while wall stress did not significantly affect its value (p=0.479).

Conclusions

Our study demonstrated that SW elastography can detect differences in myocardial stiffness in hypertensive heart and hypertrophic cardiomyopathy. Additionally, our results suggest that SW velocity is dominated by underlying myocardial tissue properties. We hypothesize that differential changes in cardiomyocytes and/or the extracellular matrix contribute to the differential myocardial stiffening in different pathologic entities of LV hypertrophy. Thus, SW elastography could provide useful novel diagnostic information in the evaluation of LV hypertrophy.

Figure A, B, C

Funding Acknowledgement

Type of funding source: None

Analysis of partial volume correction on quantification and regional heterogeneity in cardiac PET

BACKGROUND

The partial volume correction (PVC) of cardiac PET datasets using anatomical side information during reconstruction is appealing but not straightforward. Other techniques, which do not make use of additional anatomical information, could be equally effective in improving the reconstructed myocardial activity.

METHODS

Resolution modeling in combination with different noise suppressing priors was evaluated as a means to perform PVC. Anatomical priors based on a high-resolution CT are compared to non-anatomical, edge-preserving priors (relative difference and total variation prior). The study is conducted on ex vivo datasets from ovine hearts. A simulation study additionally clarifies the relationship between prior effectiveness and myocardial wall thickness.

RESULTS

Simple resolution modeling during data reconstruction resulted in over- and underestimation of activity, which hampers the absolute left ventricular quantification when compared to the ground truth. Both the edge-preserving and the anatomy-based PVC techniques improve the absolute quantification, with comparable results (Student t-test, P = .17). The relative tracer distribution was preserved with any reconstruction technique (repeated ANOVA, P = .98).

CONCLUSIONS

The use of edge-preserving priors emerged as optimal choice for quantification of tracer uptake in the left ventricular wall of the available datasets. Anatomical priors visually outperformed edge-preserving priors when the thinnest structures were of interest.

156 Shear wave propagation velocity after aortic valve closure could be a novel parameter for myocardial contractility

Funding Acknowledgements

Research Foundation (FWO) Flanders grant

Background

Shear wave imaging is a novel ultrasound technique based on the detection of transverse waves travelling through the myocardium by using high frame rate (HFR) echocardiography. These waves can be induced by an external or internal stimulus, such as aortic valve closure (AVC). The propagation velocity of shear waves is directly dependent on myocardial stiffness. It has been previously suggested in animals that the shear wave propagation velocity at AVC might be related to myocardial contractility.

Aim

The aim of this study was to validate if the shear wave propagation velocity after AVC (end-systole) is related to myocardial contractility.

Methods

Firstly, 11 healthy volunteers (age: 25 ± 4 years; male: n = 11) performed a supine bicycle exercise test. Images were taken at rest and during 25%, 50% and 66% of maximal workload, as determined by previous upright bicycle exercise testing. Secondly, 9 patients (age: 63 ± 10 years; male: n = 7) underwent a dobutamine stress echocardiography. The stress echo was negative in all patients. Images were taken at rest and after a dobutamine administration of 10µg/kg/min and 40µg/kg/min. Left ventricular (LV) parasternal long axis views were acquired with an experimental HFR ultrasound scanner (HD-PULSE) (average frame rate: 1217 ± 233fps). Apical 4-chamber views were acquired with a conventional ultrasound machine. Non-invasive single beat end-systolic elastance (Ees) was used as a measure of contractility. Acceleration maps were created from HFR-datasets by drawing a M-mode line along the midline of the interventricular septum. Shear wave propagation speed at AVC (end-systole) was calculated by measuring the slope of the wave front on the acceleration maps (Figure A).

Results

During the bicycle exercise, heart rate (61 ± 11bpm vs. 146 ± 13bpm; p < 0.001), systolic blood pressure (125 ± 12mmHg vs. 173 ± 15mmHg; p < 0.001), LV ejection fraction (55 ± 3% vs. 70 ± 5%; p < 0.001), Ees (1.8 ± 0.3mmHg/ml vs. 3.6 ± 1.0mmHg/ml; p < 0.001) and propagation velocity of the shear waves (3.3 ± 0.5m/s vs. 6.2 ± 1.7m/s; p < 0.01) (Figure B) increased significantly from rest to exercise. Likewise, dobutamine administration significantly increased the heart rate (68 ± 10bpm vs. 131 ± 14bpm; p < 0.001), LV ejection fraction (57 ± 5% vs. 74 ± 7%; p < 0.001), as well as the shear wave velocity after AVC (4.4 ± 0.6m/s vs. 7.2 ± 1.7m/s; p < 0.01) (Figure C) and Ees (2.1 ± 0.4mmHg/ml vs. 3.3 ± 0.8mmHg/ml; p < 0.001). Independent from the stressor, shear wave propagation velocity had a good and significant correlation with Ees (Figure D).

Conclusion

Shear wave propagation velocity after AVC increases with increasing level of exercise or dobutamine dose. Shear wave velocities at AVC show a good correlation with Ees. Our data indicate that end-systolic shear wave velocity is related to myocardial contractility and might therefore be a potential novel parameter for the non-invasive assessment of myocardial function.

Abstract 156 Figure.

556 Shear wave imaging using ultra-high frame rate echocardiography for the assessment of structural changes in cardiac transplant recipients

Background

Cardiac allografts undergo characteristic alterations of the extracellular matrix, including myocardial fibrosis, that contribute to functional changes, particularly diastolic dysfunction due to increased myocardial stiffness(MS). Histological examination is the gold standard for myocardial fibrosis quantification, however, it requires endomyocardial biopsies which are invasive and not without risk. Increased native T1 and extracellular volume(ECV) using CMR T1 mapping have shown good correlation with biopsy evidence of myocardial interstitial fibrosis in heart transplant(HTx) recipients. Echocardiographic shear wave(SW) elastography is an emerging approach for measuring MS in vivo. SWs occur after mechanical excitation of the myocardium, e.g. after mitral(MVC) and aortic valve closure(AVC), and their propagation velocity is directly related to MS, thus providing an opportunity to assess stiffness at end-diastole(ED) and end-systole(ES).

Purpose

The aim was to investigate if natural shear wave velocities increase with the degree of diffuse myocardial fibrosis in HTx recipients.

Methods

We prospectively enrolled 22 HTx patients (8.8 ± 5.9 years post-HTx) that underwent CMR during their annual check-up. We performed SW elastography in parasternal long axis views of the left ventricle(LV) using an experimental scanner (HD-PULSE) equipped with a clinical phased array transducer (Samsung Medison P2-5AC) at 1100 ± 250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC and AVC was measured as the slope on the M-mode acceleration map(FigureA). All patients underwent right heart catheterization on the same day for the measurement of pulmonary capillary wedge pressure(PCWP), as surrogate for LV filling pressure. The CMR protocol consisted of standard sequences including native and post-contrast T1 mapping. To evaluate diffuse myocardial fibrosis, native T1 and ECV were measured in the anteroseptal wall over all available short-axis slices.

Results

We found good correlations between SW velocities at ED and both myocardial T1 (r = 0.8,p < 0.001,FigureB) and ECV (r = 0.6,p < 0.05,FigureC) measured with CMR. Similarly, we found significant correlations between SW velocities at ES and T1 (r = 0.7,p < 0.005) and ECV (r = 0.5,p < 0.05), respectively. Furthermore, we observed a significant correlation between SW velocities at ED and PCWP (r = 0.6,p < 0.05).

Conclusions

Both end-diastolic and end-systolic shear wave velocities showed a good correlation with CMR defined myocardial fibrosis in cardiac transplant patients. Shear wave velocities at end-diastole correlated with invasively-determined left ventricular filling pressure, reflecting the impact of the fibrous changes on the left ventricular diastolic function. These results suggest the potential of cardiac shear wave elastography for the assessment of structural changes in cardiac transplant recipients.

Abstract 556 Figure.

1181 A novel insight into pathophysiology of hypertrophic cardiomyopathy using simultaneous three-dimensional volume-strain loops

Funding Acknowledgements

Supported with a scholarship by the Greek State Scholarship Foundation (IKY).

Background

Strain assessment offers a robust evaluation of myocardial mechanics and systolic function, however reporting only peak strain values in hypertrophic cardiomyopathy (HCM) may impose limitations in the conception of its complex remodeling. Therefore, combined plotting of deformation parameters against other indices [e.g. arterial pressure, left ventricular (LV) volume] might offer additional insights into the pathophysiology of the disease.

Purpose

Aim of this study was i) to apply strain-volume loops in HCM based on simultaneous frame-by-frame strain and volume changes’ recordings acquired by means of three-dimensional (3D) speckle tracking imaging and ii) to take advantage of the previous methodology to gain further insights into HCM pathophysiology.

Methods

We included 40 HCM patients (54.1 ± 14.3 years, 82.5% male, maximum wall thickness 19.3 ± 4.8mm) who have consecutively undergone 3D-speckle tracking echocardiography and cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). Values of 3D strain were plotted vs. volume for each frame to build a strain–volume loop. Peak of radial, longitudinal, and circumferential systolic strain (Rsp, Lsp, and Csp, respectively), systolic slopes of the loops (RsSl, LsSl, CsSl), and strain to end-diastolic volume (EDV) ratio (Rs/V, Ls/V, Cs/V) were computed for the analysis (panel A). Additionally, burden of fibrosis (percentage of LV mass) was defined by LGE extent (>5 standard deviations compared to nulled myocardium) in CMR slices.

Results

All HCM patients had preserved EF (60.5 ± 5,7%), while 16 (40%) had LV outflow tract obstruction (LVOTO > 30 mm Hg at rest). Mean LV mass index was 78.9 ± 14.5 g (evaluated by 3D echocardiography). LGE was observed in 23 patients (57.5%) occupying 5.2 ± 4.5% of LV mass. Concerning strain-volume loops the following values were recorded for radial (Rsp 30.8 ± 9.8%, RsSl 0.4 ± 0.13 and Rs/V 0.25 ± 0.09), longitudinal (Lsp -9.4 ± 3.7%, LsSl 0.12 ± 0.06 and Ls/V 0.08 ± 0.04) and circumferential deformation (Csp -14.2 ± 3.5%, CsSl 0.18 ± 0.05 and Cs/V 0.11 ± 0.03). Among typical HCM characteristics tested (LV mass, LVOTO and LGE), only LV mass presented significant correlations with LsSl (r=-0.41, p < 0.01). Interestingly, HCM patients with smaller LVMI and without LGE presented steeper and narrower (difference between systolic and diastolic strain for the same volume) longitudinal strain-volume loops compared to patients with larger LVMIs and fibrosis (panel B).

Conclusions

Strain-volume loop is an innovative application of 3D deformation imaging in HCM. According to this new non-invasive method, increase of LVMI in HCM is accompanied by less longitudinal contribution to stroke volume, whereas absence of fibrosis and severe hypertrophy is accompanied by better systolic-diastolic coupling.

Abstract 1181 Figure.

P984 A head-to-head comparison between 2D and 3D segmental strain parameters in hypertrophic cardiomyopathy

Funding Acknowledgements

Supported with a scholarship by the Greek State Scholarship Foundation (IKY).

Background

Previous studies have suggested that in normal and ischemic hearts three- (3D) and two-dimensional (2D) strain values present a moderate agreement which is prone to technical considerations. However, the level of agreement between 2D and 3D-strain imaging has never been adequately addressed in hypertrophic hearts, nor has it been validated against a "ground truth". Especially in hypertrophic cardiomyopathy (HCM), the magnitude and eccentricity of hypertrophy set additional challenges in standardization and measurement of regional 3D deformation parameters.

Purpose

Aims of this study were i) to investigate the consistency between 3D and 2D regional deformation parameters in HCM and ii) to test their accuracy in identifying regional fibrosis as this is defined by late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR).

Methods

We included 40 HCM patients (54.1 ± 14.3 years, 82.5% male, maximum wall thickness 19.3 ± 4.8mm) who have consecutively undergone 2D-,3D-speckle tracking echocardiography and CMR. Segmental circumferential (SCS) and longitudinal (SLS) strain have been calculated from 2D acquisitions and 3D full volume data, where additionally radial (SRS) and area (SAS) strain have been extracted using an 18 segment left ventricle model. Accordingly, segmental fibrosis was defined by LGE in corresponding CMR slices.

Results

Out of 720 segments evaluated, 134 (19.7%) were enhanced and 95(13.2%) thickened (thickness > 12 mm). Two dimensional LS and CS analysis was feasible in 719 (99.9%) and 678 (94.2%) segments respectively, while 686 segments (95.3%) were appropriate for 3D tracking. 3D_SLS values were -7.9 ± 6.8% less negative compared to 2D_SLS values [level of agreement (LOA)(-21.1-5.4%)], while the bias for SCS values was even higher -8.5 ± 8.6 [LOA(-25.4-8.4%)]. Absolute agreement between 2D and 3D deformation imaging modalities was poor to moderate [Intra-class Correlation Coefficient (ICC)= 0.46, 95%CI (0.15-0.68), p < 0.0005 for SLS and ICC = 0.19, 95%CI(0.07-0.38), p < 0.0005 for SCS] (Panel A). Following regression analysis, regional thickness was the only segmental factor to influence the correlation between 3D and 2D_SLS [R2 = 0.504, B = 0.33, 95%CI(0.22-0.44), p < 0.0005)], without, however, being a significant regressor for the other 2D vs 3D correlations. Among deformation indices, 2D_SLS showed the best area under the curve [(AUC)=0.78, 95%CI(0.75-0.81), p < 0.0005] to detect segmental fibrosis identified by CMR LGE, with 3D_SLS, 3D_SAS and 3D_SRS showing similar AUC (0.65) and 3D_SLS presenting the highest specificity [93.1%, 95%CI(90.6-95.1)] (Panel B).

Conclusions

In HCM, 2D and 3D deformation parameters are not interchangeable, showing modest agreement. Thickness and tracking algorithm calculating assumptions seem to induce this inconsistency. Among HCM patients, 2D_SLS remains the most accurate strain parameter to detect regional fibrosis.

Abstract P984 Figure.

P975 Echocardiography and nuclear medicine imaging techniques are insufficient for scar detection in patients referred for cardiac resynchronization therapy

Funding Acknowledgements

The study was supported by Center for Cardiological Innovation

Background

Many patients referred for cardiac resynchronization therapy (CRT) do not respond to the treatment. Scar either in septum or the left ventricular (LV) lateral wall, as well as global scar burden, influence the outcome negatively. Preoperative scar assessment is therefore recommended in this patient group. Late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) is considered reference standard for scar detection, but is not always available.

Purpose

To investigate the ability of advanced echocardiographic and nuclear imaging techniques to detect septal and left ventricular (LV) lateral wall scar in patients referred for CRT, compared to late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR).

Methods

Scar was quantified as percentage segmental LGE in 131 patients (age 66 ± 10, 66% male, QRS-width 164 ± 17ms) referred for CRT, 92% with left bundle branch block (LBBB). Longitudinal strain was assessed by speckle tracking echocardiography in 130 patients (641 septal and 630 LV lateral wall segments). Wall motion score index (WMSI) was assessed visually in all patients by an experienced operator, and graded from one to four. Glucose metabolism was assessed by 18F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) in 52 patients. Perfusion was assessed in 46 patients by either 13N-ammonia PET (n = 32) or Single Photon Emission Computed Tomography (SPECT) (n = 14). Metabolism and perfusion were reported as percentages of the segment with maximum tracer uptake. The ability of each parameter to identify scar was evaluated with receiver operating characteristic (ROC) curves with calculation of area under the curve (AUC) and 95% confidence interval (CI). AUC≥0.800 was considered reasonable agreement with LGE.

Results

Scar was present in 574 of total 2090 interpretable segments (79% ischemic etiology). Globally, perfusion (AUC = 0.845, 95% CI 0.777-0.914) and glucose metabolism (AUC = 0.807, 95% CI 0.758-0.855) adequately detected transmural scars, but not smaller scars (all AUC < 0.800). Echocardiographic parameters failed to detect global scars irrespective of size (all AUC < 0.800). However, the associations between echocardiographic/nuclear parameters and scars were highly dependent on myocardial region. In the LV lateral wall, glucose metabolism precisely detected transmural scars (AUC = 0.958, 95% CI 0.902-1.00) and WMSI proved reasonable agreement (AUC = 0.812, 95% CI 0.737-0.887), while the rest of the parameters did not (all AUC < 0.800). Smaller scars in this region was not detected by any parameter tested (all AUC < 0.800). No parameter adequately detected septal scars, not even those with transmural involvement (all AUC < 0.800) (Figure).

Conclusions

Neither echocardiographic nor nuclear imaging techniques can replace LGE-CMR in scar assessment prior to CRT. Septum is especially challenging, explained by LBBB-induced reduction in strain, metabolism and perfusion in this region.

Abstract P975 Figure. Detection of transmural septal scar