Extent of myocardial viability predicts response to biventricular pacing in ischemic cardiomyopathy

Cardiac Resynchronisation Therapy and Cellular Bioenergetics: Effects Beyond Chamber Mechanics

Cardiac resynchronisation therapy is a cornerstone in the treatment of advanced dyssynchronous heart failure. However, despite its widespread clinical application, precise mechanisms through which it exerts its beneficial effects remain elusive. Several studies have pointed to a metabolic component suggesting that, both in concert with alterations in chamber mechanics and independently of them, resynchronisation reverses detrimental changes to cellular metabolism, increasing energy efficiency and metabolic reserve. These actions could partially account for the existence of responders that improve functionally but not echocardiographically. This article will attempt to summarise key components of cardiomyocyte metabolism in health and heart failure, with a focus on the dyssynchronous variant. Both chamber mechanics-related and -unrelated pathways of resynchronisation effects on bioenergetics – stemming from the ultramicroscopic level – and a possible common underlying mechanism relating mechanosensing to metabolism through the cytoskeleton will be presented. Improved insights regarding the cellular and molecular effects of resynchronisation on bioenergetics will promote our understanding of non-response, optimal device programming and lead to better patient care.

Uniqueness of local myocardial strain patterns with respect to activation time and contractility of the failing heart: a computational study

Background

Myocardial deformation measured by strain is used to detect electro-mechanical abnormalities in cardiac tissue. Estimation of myocardial properties from regional strain patterns when multiple pathologies are present is therefore a promising application of computer modelling. However, if different tissue properties lead to indistinguishable strain patterns (‘degeneracy’), the applicability of any such method will be limited. We investigated whether estimation of local activation time (AT) and contractility from myocardial strain patterns is theoretically possible.

Methods

For four different global cardiac pathologies local myocardial strain patterns for 1025 combinations of AT and contractility were simulated with a computational model (CircAdapt). For each strain pattern, a cohort of similar patterns was found within estimated measurement error using the sum of least-squared differences. Cohort members came from (1) the same pathology only, and (2) all four pathologies. Uncertainty was calculated as accuracy and precision of cohort members in parameter space. Connectedness within the cohorts was also studied.

Results

We found that cohorts drawn from one pathology had parameters with adjacent values although their distribution was neither constant nor symmetrical. In comparison cohorts drawn from four pathologies had disconnected components with drastically different parameter values and accuracy and precision values up to three times higher.

Conclusions

Global pathology must be known when extracting AT and contractility from strain patterns, otherwise degeneracy occurs causing unacceptable uncertainty in derived parameters.

Electronic supplementary material

The online version of this article (10.1186/s12938-018-0614-1) contains supplementary material, which is available to authorized users.

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

INTRODUCTION

Cardiac resynchronization therapy (CRT) has emerged as one of the few effective treatments for heart failure. However, up to 50% of patients derive no benefit. Suboptimal left ventricle (LV) lead position is a potential cause of poor outcomes while targeted lead deployment has been associated with enhanced response rates. Image-fusion guidance systems represent a novel approach to CRT delivery, allowing physicians to both accurately track and target a specific location during LV lead deployment.

AREAS COVERED

This review will provide a comprehensive evaluation of how to define the optimal pacing site. We will evaluate the evidence for delivering targeted LV stimulation at sites displaying favorable viability or advantageous mechanical or electrical properties. Finally, we will evaluate several emerging image-fusion guidance systems which aim to facilitate optimal site selection during CRT.

EXPERT COMMENTARY

Targeted LV lead deployment is associated with reductions in morbidity and mortality. Assessment of tissue characterization and electrical latency are critical and can be achieved in a number of ways. Ultimately, the constraints of coronary sinus anatomy have forced the exploration of novel means of delivering CRT including endocardial pacing which hold promise for the future of CRT delivery.

Current role of echocardiography in cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure and left ventricular systolic dysfunction. Patients are usually assessed by echocardiography, which provides a number of anatomical and functional information used for cardiac dyssynchrony assessment, prognostic stratification, identification of the optimal site of pacing in the left ventricle, optimization of the CRT device, and patient follow-up. Compared to other cardiac imaging techniques, echocardiography has the advantage to be non-invasive, repeatable, and safe, without exposure to ionizing radiation or nefrotoxic contrast. In this article, we review current evidence about the role of echocardiography before, during, and after the implantation of a CRT device.

Abnormal diastolic function underlies the different beneficial effects of cardiac resynchronization therapy on ischemic and non-ischemic cardiomyopathy

OBJECTIVES:

To investigate the association between diastolic function and the different beneficial effects of cardiac resynchronization therapy in patients with heart failure due to different causes.

METHODS:

The 104 enrolled patients were divided into an ischemic cardiomyopathy group (n=27) and a non-ischemic cardiomyopathy group (n=77) according to the cause of heart failure. Before implantation, left ventricular diastolic function was evaluated in all patients using echocardiography. After six months of follow-up, the beneficial effects of cardiac resynchronization therapy were evaluated using a combination of clinical symptoms and echocardiography parameters.

RESULTS:

The ischemic cardiomyopathy group included significantly more patients with restrictive filling than the non-ischemic cardiomyopathy group. The response rate after the implantation procedure was significantly higher in the non-ischemic cardiomyopathy group than in the ischemic cardiomyopathy group. Degrees of improvement in echocardiography parameters were significantly greater in the non-ischemic cardiomyopathy group than in the ischemic cardiomyopathy group. Multivariate regression analysis showed that a restrictive filling pattern was an independent factor that influenced responses to cardiac resynchronization therapy.

CONCLUSIONS:

This study again confirmed that the etiology of heart failure affects the beneficial effects of cardiac resynchronization therapy and a lower degree of improvement in ventricular systolic function and remodelling was observed in ischemic cardiomyopathy patients than in non-ischemic cardiomyopathy patients. In addition, systolic heart failure patients with severe diastolic dysfunction had poor responses to cardiac resynchronization therapy. Ischemic cardiomyopathy patients exhibited more severe diastolic dysfunction than non-ischemic cardiomyopathy patients, which may be a reason for the reduced beneficial effect of cardiac resynchronization therapy.

Is speckle tracking actually helpful for cardiac resynchronization therapy?

What is the specific role of echocardiography in cardiac resynchronization therapy (CRT)? CRT has proven to be highly effective for improving symptoms and survival of patients with advanced heart failure (HF) and wide QRS. However, a significant minority of patients do not respond favorably to CRT on the basis of standard clinical selection criteria, including the electrocardiographic QRS width. Subsequently, echocardiographic assessment of left ventricular (LV) dyssynchrony has been considered useful for CRT for selected responders, but findings by multicenter studies suggest that its predictive value was not sufficiently robust to replace routine selection criteria for CRT. A more recent approach, however, using speckle-tracking echocardiography yields more accurate quantification of regional wall contraction. Speckle-tracking approaches have therefore generated a great deal of interest about their clinical applications for CRT. Although reports on speckle tracking have not been included in any recommendations as to whether patients should undergo CRT based on the current guidelines, speckle tracking can play an important supplementary part in CRT on the basis of a case-by-case clinical decision for challenging cases. Here, we review the strengths of speckle-tracking methods, and their current potential for clinical use in CRT.

Three-dimensional echocardiographic optimization improves outcome in cardiac resynchronization therapy compared to ECG optimization: a randomized comparison

AIMS

There is little consensus on optimal atrioventricular (AV) and ventricular-to-ventricular (VV) intervals in cardiac resynchronization therapy (CRT). The aim of this study was to examine a novel combination of Doppler echocardiography (DE) and three-dimensional echocardiography (3DE) for individualized AV- and VV-interval optimization compared to conventional electrocardiogram (ECG) optimization.

METHODS

In this double-blind, randomized controlled trial, 77 patients (male: 57, age: 68 ± 10 years) with severely reduced ejection fraction (EF), New York Heart Association (NYHA) class III or IV, and wide QRS complex (>120 ms) have been included. Patients were randomized to either AV- and VV-interval optimization using DE and 3DE (group 1, n = 39) or ECG (group 2, n = 38). 3DE was performed in all patients for the evaluation of left ventricular (LV) dimensions, EF and systolic dyssynchrony index (SDI), and NYHA class obtained before CRT and after 3 months. Primary endpoint of the study was clinical response to CRT, defined as a reduction of NYHA class by ≥1 score. Secondary endpoints were change of EF, LV volumes, and SDI.

RESULTS

There were significantly more responders in group 1 (82%) than in group 2 (58%, P = 0.021). Similarly, group 1 showed a larger increase in EF (7.0 ± 6.0% vs 3.4 ± 5.6%, P = 0.015) and a more pronounced reduction of SDI (-4.5 ± 5.9% vs -1.5 ± 5.6%, P = 0.039) than group 2.

CONCLUSION

Compared with conventional ECG optimization, this novel echocardiographic optimization protocol resulted in a significantly higher response rate, improved LV systolic function, and may be used to select the optimal AV and VV intervals in CRT.

Assesment of myocardial ischemia by combination of tissue synchronisation imaging and dobutamine stress echocardiography

BACKGROUND AND OBJECTIVES

Dobutamine stress echocardiography (DSE) is an important non-invasive imaging method for evaluating ischemia. However, wall motion interpretation can be impaired by the experience level of the interpreter and the subjectivity of the visual assessment. In our study we aimed to combine DSE and tissue syncronisation imaging to increase sensitivity for detecting ischemia.

SUBJECTS AND METHODS

50 patients with indications for DSE were included in the study. In 25 patients we found DSE positive for ischemia and in the other 25 patients we found it to be negative. The negative group was accepted as the control group. There was no significant difference in terms of risk factors and echocardiographic parameters between the two groups, except for wall motion scores. In both groups, left ventricular dyssychrony was accepted as the difference between time to peak systolic velocity (Ts) in the reciprocal four couple of non-apical segments at rest and during peak stress. Timings were corrected for heart rate. We compared the differences of the dyssynchronisation value at rest and during peak stress to determine the distinctions within the groups and between the groups of DSE positive and negative patients.

RESULTS

We found that stress and ischemia did not create any significant difference over the left intraventricular dyssynchrony with DSE, although at the segmenter level it prolonged the time to peak systolic velocity (p<0.05). These alterations did not show any significant difference between positive and negative DSE groups.

CONCLUSION

As a result, this segmenter dyssynchrony and the time to peak systolic velocity, which is corrected for heart rate, did not enhance any new value over DSE for detecting ischemia.

Acute beneficial hemodynamic effects of a novel 3D-echocardiographic optimization protocol in cardiac resynchronization therapy

BACKGROUND

Post-implantation therapies to optimize cardiac resynchronization therapy (CRT) focus on adjustments of the atrio-ventricular (AV) delay and ventricular-to-ventricular (VV) interval. However, there is little consensus on how to achieve best resynchronization with these parameters. The aim of this study was to examine a novel combination of doppler echocardiography (DE) and three-dimensional echocardiography (3DE) for individualized optimization of device based AV delays and VV intervals compared to empiric programming.

METHODS

25 recipients of CRT (male: 56%, mean age: 67 years) were included in this study. Ejection fraction (EF), the primary outcome parameter, and left ventricular (LV) dimensions were evaluated by 3DE before CRT (baseline), after AV delay optimization while pacing the ventricles simultaneously (empiric VV interval programming) and after individualized VV interval optimization. For AV delay optimization aortic velocity time integral (AoVTI) was examined in eight different AV delays, and the AV delay with the highest AoVTI was programmed. For individualized VV interval optimization 3DE full-volume datasets of the left ventricle were obtained and analyzed to derive a systolic dyssynchrony index (SDI), calculated from the dispersion of time to minimal regional volume for all 16 LV segments. Consecutively, SDI was evaluated in six different VV intervals (including LV or right ventricular preactivation), and the VV interval with the lowest SDI was programmed (individualized optimization).

RESULTS

EF increased from baseline 23±7% to 30±8 (p<0.001) after AV delay optimization and to 32±8% (p<0.05) after individualized optimization with an associated decrease of end-systolic volume from a baseline of 138±60 ml to 115±42 ml (p<0.001). Moreover, individualized optimization significantly reduced SDI from a baseline of 14.3±5.5% to 6.1±2.6% (p<0.001).

CONCLUSIONS

Compared with empiric programming of biventricular pacemakers, individualized echocardiographic optimization with the integration of 3-dimensional indices into the optimization protocol acutely improved LV systolic function and decreased ESV and can be used to select the optimal AV delay and VV interval in CRT.

[Three-dimensional imaging in cardiac resynchronization therapy]

Cardiac resynchronization therapy improves clinical symptoms and prognosis of heart failure patients. However, it has been shown that up to 40% of patients do not respond to this therapy. Three main determinants of cardiac resynchronization therapy response have been identified: left ventricular dyssynchrony, left ventricular lead position, and extent and location of myocardial scar tissue. Two-dimensional echocardiography is the first imaging technique to evaluate patients who may be candidates for cardiac resynchronization therapy. However, a multimodality approach based on 3-dimensional imaging techniques may provide a more comprehensive evaluation of these patients by combining the assessment of the aforementioned pathophysiological determinants of cardiac resynchronization therapy response.

Cardiac Resynchronization Therapy as a Therapeutic Option in Patients With Moderate-Severe Functional Mitral Regurgitation and High Operative Risk

Background—

Functional mitral regurgitation (MR) is a common finding in heart failure patients with dilated cardiomyopathy and has important prognostic implications. However, the increased operative risk of these patients may result in low referral or high denial rate for mitral valve surgery. Cardiac resynchronization therapy (CRT) has been shown to have a favorable effect on MR. Aims of this study were to (1) evaluate CRT as a therapeutic option in heart failure patients with functional MR and high operative risk and (2) investigate the effect of MR improvement after CRT on prognosis.

Methods and Results—

A total of 98 consecutive patients with moderate-severe functional MR and high operative risk underwent CRT according to current guidelines. Echocardiography was performed at baseline and 6-month follow-up; severity of MR was graded according to a multiparametric approach. Significant improvement of MR was defined as a reduction ≥1 grade. All-cause mortality was assessed during follow-up (median 32 [range 6.0 to 116] months). Thirteen patients (13%) died before 6-months follow-up. In the remaining 85 patients, significant reduction in MR was observed in all evaluated parameters. In particular, 42 patients (49%) improved ≥1 grade of MR and were considered MR improvers. Survival was superior in MR improvers compared to MR nonimprovers (log rank P <0.001). Mitral regurgitation improvement was an independent prognostic factor for survival (hazard ratio 0.35, confidence interval 0.13 to 0.94; P =0.043).

Conclusions—

Cardiac resynchronization therapy is a potential therapeutic option in heart failure patients with moderate-severe functional MR and high risk for surgery. Improvement in MR results in superior survival after CRT.

Lead positioning strategies to enhance response to cardiac resynchronization therapy

Left ventricular lead position is one of the main determinants of CRT response. There are several approaches in LV lead positioning that include favoring an optimal anatomical position or targeting either the segment with maximal mechanical dyssynchrony or a region with maximal electrical delay. The conventional LV lead implantation faces several technical difficulties that may prevent the obtaining of a stable position and good performance of the LV lead without phrenic nerve stimulation. In addition, implant of the LV pacing lead in areas with myocardial scar may result in less than optimal cardiac resynchronization. Several strategies have been proposed to overcome all these obstacles including multimodality cardiac imaging to help in preprocedural or intraprocedural identification of the latest activated areas of the LV and the potential anatomical constraints. In selected patients, the surgical implant may be a solution to overcome these constraints. In the future, LV endocardial or epicardial multisite pacing may deliver an enhanced response to CRT.

[Cardiac resynchronization therapy: preoperative screening. How can we reliably predict response to CRT?]

Cardiac resynchronization therapy (CRT) is an established therapy for patients with advanced heart failure, depressed left ventricular function, and wide QRS complex. However, about 30 to 45% of patients do not respond to CRT. Assuming that the main therapeutic action of CRT is the correction of dyssynchronous myocardial contraction, a plethora of echocardiographic dyssynchrony parameters have been proposed to improve the prediction of response to CRT. However, one multicenter study has recently questioned the utility of any of these indexes. This review delineates the various causes of non-response to CRT, explains the different levels and mechanisms of dyssynchrony and gives a critical overview of currently available echocardiographic techniques for assessment of dyssynchrony. Based upon a discussion of the evidence coming from randomized multicenter studies and against the background of national and international cardiac societies' guideline recommendations on CRT, a rational basis for the evaluation of patients for CRT is proposed.

A prospective pilot study to evaluate the relationship between acute change in left ventricular synchrony after cardiac resynchronization therapy and patient outcome using a single-injection gated SPECT protocol

BACKGROUND

There are ongoing efforts to optimize patient selection criteria for cardiac resynchronization therapy (CRT). In this regard, the relationship between acute change in left ventricular synchrony (LV) after CRT and patient outcome remains undefined.

METHODS AND RESULTS

A novel protocol was designed to evaluate acute change in left LV synchrony after CRT using phase analysis of standard gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging with a single injection of radiotracer and prospectively applied to 44 patients undergoing CRT. Immediately after CRT, 18 (41%), 11 (25%), and 15 (34%) patients had an improvement, no change, or a worsening in LV synchrony. An algorithm incorporating the presence of baseline dyssynchrony, myocardial scar burden, and lead concordance predicted acute improvement or no change in LV synchrony with 72% sensitivity, 93% specificity, 96% positive predictive value, and 64% negative predictive value and had 96% negative predictive value for acute deterioration in synchrony. Over a follow-up period of 9.6 ± 6.8 months, patients who had an acute deterioration in synchrony after CRT had a higher composite event rate of death, heart failure hospitalizations, appropriate defibrillator discharges, and CRT device deactivation for worsening heart failure symptoms, compared with patients who had an improvement or no change [hazard ratio, 4.6 (1.3 to 16.0); log rank test; P=0.003].

CONCLUSIONS

In this single-center pilot study, phase analysis of gated SPECT was successfully used to predict acute change in LV synchrony and patient outcome after CRT.

Criteria for patient selection in cardiac resynchronization therapy

Since the implementation of cardiac resynchronization therapy (CRT) the prognosis of patients with severe heart failure has been improved owing to a reduction in morbidity and mortality rates, as several multicenter trials have shown. However, several patients treated by CRT still lack improvement or even deteriorate during therapy. In some of them, this might be due to the severity and progression of chronic heart failure. In others, the criteria for the indication of CRT and/or optimized device programming might have not been met. Thus, one important option to improve CRT outcome is to improve CRT patient selection. A lot of publications describing various methods identifying a positive or negative prediction of CRT have been released. In summary, decision making based on all these partly contradictory publications indicate a strong need for guidelines for the use of such expensive therapy. The purpose of this article is to give an overview of CRT and summarize the different methods and the limitations of CRT patient selection parameters. With the focus of the different guidelines, this article tries to give an appropriate overview and aid decision making in CRT patients, including a short view of possible new indications.

Electrocardiogram-gated 18F-FDG PET/CT hybrid imaging in patients with unsatisfactory response to cardiac resynchronization therapy: initial clinical results

The present study aimed to distinguish responders to cardiac resynchronization therapy (CRT) from nonresponders, using electrocardiogram-gated 18F-FDG PET/CT.

METHODS

Seven consecutive CRT nonresponders were included in the study, along with 7 age- and sex-matched CRT responders, serving as reference material. Therapy response was defined as clinical improvement (≥1 New York Heart Association class) and evidence of reverse remodeling. Besides PET/CT, we measured brain natriuretic peptide levels and assessed dyssynchrony using transthoracic echocardiography.

RESULTS

Compared with nonresponders, CRT responders showed significant differences in the declines of left-ventricular end-systolic volume and brain natriuretic peptide and in left-ventricular dyssynchrony (global left-ventricular entropy), extent of the myocardial scar burden, and biventricular pacemaker leads positioned within viable myocardial regions. Among the nonresponders, further therapy management was guided by the PET/CT results in 4 of 7 patients.

CONCLUSION

Cardiac hybrid imaging using gated 18F-FDG PET/CT enabled the identification of potential reasons for nonresponse to CRT therapy, which can guide subsequent therapy.

Prediction of Cardiac Resynchronization Therapy Response

Background— Left ventricular (LV) fibrosis is important for the response to cardiac resynchronization therapy (CRT). Calibrated integrated backscatter derived by 2D echocardiography quantifies myocardial ultrasound reflectivity, which may provide a surrogate of LV fibrosis. The aim of the study was first, to investigate the relation of myocardial ultrasound reflectivity assessed with calibrated integrated backscatter on CRT response, and second, to explore the “myocardial ultrasound reflectivity–CRT response” relation in patients with ischemic and nonischemic heart failure (HF).

Methods and Results— One hundred fifty-nine patients with HF referred for CRT underwent an extensive echocardiographic evaluation at baseline and at 6-month follow-up. LV dyssynchrony was derived from speckle-tracking analysis. Calibrated integrated backscatter was obtained from the parasternal long-axis view. The mean value of calibrated integrated backscatter of the anteroseptal and posterior wall was used to estimate myocardial ultrasound reflectivity. CRT response was defined as reduction ≥15% of LV end-systolic volume. At baseline, LV dyssynchrony was significantly larger in responders as compared with nonresponders (188�96 ms versus 115�68 ms, P <0.001), and CRT responders showed less myocardial ultrasound reflectivity as compared with nonresponders (−20.8�3.0 dB versus −17.0�3.0 dB, P <0.001). In multivariable logistic regression analysis, independent predictors for CRT response were LV dyssynchrony, renal function, and myocardial ultrasound reflectivity. Importantly, myocardial ultrasound reflectivity provided an incremental value to CRT response (χ 2 change=40, P <0.001). Considering patients with ischemic HF, the only independent predictor of CRT response was myocardial ultrasound reflectivity, whereas in patients with nonischemic HF, independent predictors of LV reverse remodeling were myocardial ultrasound reflectivity, LV dyssynchrony, and renal function.

Conclusions— Assessment of myocardial ultrasound reflectivity is important in the prediction of CRT response in ischemic and nonischemic patients.

Usefulness and limitation of dobutamine stress echocardiography to predict acute response to cardiac resynchronization therapy

BACKGROUND

It has been hypothesized that a long-term response to cardiac resynchronization therapy (CRT) could correlate with myocardial viability in patients with left ventricular (LV) dysfunction. Contractile reserve and viability in the region of the pacing lead have not been investigated in regard to acute response after CRT.

METHODS

Fifty-one consecutive patients with advanced heart failure, LV ejection fraction <or= 35%, QRS duration > 120 ms, and intraventricular asynchronism >or= 50 ms were prospectively included. The week before CRT implantation, the presence of viability was evaluated using dobutamine stress echocardiography. Acute responders were defined as a >or=15% increase in LV stroke volume.

RESULTS

The average of viable segments was 5.8 +/- 1.9 in responders and 3.9 +/- 3 in nonresponders (P = 0.03). Viability in the region of the pacing lead had an excellent sensitivity (96%), but a low specificity (56%) to predict acute response to CRT. Mitral regurgitation (MR) was reduced in 21 patients (84%) with acute response. The presence of MR was a poor predictor of response (sensibility 93% and specificity 17%). However, combining the presence of MR and viability in the region of the pacing lead yields a sensibility (89%) and a specificity (70%) to predict acute response to CRT.

CONCLUSION

Myocardial viability is an important factor influencing acute hemodynamic response to CRT. In acute responders, significant MR reduction is frequent. The combined presence of MR and viability in the region of the pacing lead predicts acute response to CRT with the best accuracy.

Impact of left ventricular size on tissue Doppler and longitudinal strain by speckle tracking for assessing wall motion and mechanical dyssynchrony in candidates for cardiac resynchronization therapy

BACKGROUND

Myocardial dysfunction and left ventricular (LV) geometry deformation may reduce the accuracy of tissue Doppler imaging (TDI) in assessing myocardial contractility.

METHODS

In 92 patients with heart failure who underwent cardiac resynchronization therapy (CRT), we assessed the impact of LV end-diastolic volume on the accuracy of peak longitudinal velocity (TDI) and strain (epsilon(L) by speckle tracking) to assess regional wall motion and LV dyssynchrony.

RESULTS

Peak-epsilon correlated to normal (-13% +/- 6%, n = 259), hypokinetic (-10% +/- 5%, n = 347), and akinetic (-7% +/- 5%, n = 498, P < .0001) wall motion independent of LV size. In contrast, velocity failed to distinguish normal from dysfunctional segments in patients with severe LV dilatation (end-diastolic volume > 250 mL). The 12 standard deviation of time to peak systolic velocity and the opposing septal-lateral wall delay by strain and TDI failed to predict response to CRT, whereas the 12 segment standard deviation of time to peak epsilon correlated to end-systolic volume reduction (r = -0.39, P < .001).

CONCLUSION

Accuracy of TDI in assessing LV wall regional motion is limited in severely dilated ventricles and probably affects LV dyssynchrony measurement.

The effects of aetiology on outcome in patients treated with cardiac resynchronization therapy in the CARE-HF trial

AIMS

Cardiac dyssynchrony is common in patients with heart failure, whether or not they have ischaemic heart disease (IHD). The effect of the underlying cause of cardiac dysfunction on the response to cardiac resynchronization therapy (CRT) is unknown. This issue was addressed using data from the CARE-HF trial.

METHODS AND RESULTS

Patients (n = 813) were grouped by heart failure aetiology (IHD n = 339 vs. non-IHD n = 473), and the primary composite (all-cause mortality or unplanned hospitalization for a major cardiovascular event) and principal secondary (all-cause mortality) endpoints analysed. Heart failure severity and the degree of dyssynchrony were compared between the groups by analysing baseline clinical and echocardiographic variables. Patients with IHD were more likely to be in NYHA class IV (7.5 vs. 4.0%; P = 0.03) and to have higher NT-proBNP levels (2182 vs. 1725 pg/L), indicating more advanced heart failure. The degree of dyssynchrony was more pronounced in patients without IHD (assessed using mean QRS duration, interventricular mechanical delay, and aorta-pulmonary pre-ejection time). Left ventricular ejection fraction and left ventricular end-systolic volume improved to a lesser extent in the IHD group (4.53 vs. 8.50% and -35.68 vs. -58.52 cm(3)). Despite these differences, CRT improved all-cause mortality, NYHA class, and hospitalization rates to a similar extent in patients with or without IHD.

CONCLUSION

The benefits of CRT in patients with or without IHD were similar in relative terms in the CARE-HF study but as patients with IHD had a worse prognosis, the benefit in absolute terms may be greater.

Impact of contractile reserve on acute response to cardiac resynchronization therapy

Background

Cardiac resynchronization therapy (CRT) provides benefit for congestive heart failure, but still 30% of patients failed to respond to such therapy. This lack of response may be due to the presence of significant amount of scar or fibrotic tissue at myocardial level. This study sought to investigate the potential impact of myocardial contractile reserve as assessed during exercise echocardiography on acute response following CRT implantation.

Methods

Fifty-one consecutive patients with heart failure (LV ejection fraction 27% ± 5%, 67% ischemic cardiomyopathy) underwent exercise Doppler echocardiography before CRT implantation to assess global contractile reserve (improvement in LV ejection fraction) and local contractile reserve in the region of the LV pacing lead (assessed by radial strain using speckle tracking analysis). Responders were defined by an increase in stroke volume ≥ 15% after CRT.

Results

Compared with nonresponders, responders (25 patients) showed a greater exercise-induced increase in LV ejection fraction, a higher degree of mitral regurgitation and a significant extent of LV dyssynchrony. The presence of contractile reserve was directly related to the acute increase in stroke volume (r = 0.48, p < 0.001). Baseline myocardial deformation as well as contractile reserve in the LV pacing lead region was greater in responders during exercise than in nonresponders (p < 0.0001).

Conclusion

The present study showed that response to CRT largely depends not only on the extent of LV dyssynchrony and the severity of mitral regurgitation but also on the presence of contractile reserve.

Automatic global and regional phase analysis from gated myocardial perfusion SPECT imaging: application to the characterization of ventricular contraction in patients with left bundle branch block

Although many patients with heart failure benefit from cardiac resynchronization therapy (CRT), predicting which patients will respond to CRT remains challenging. Recent evidence suggests that the analysis of mechanical dyssynchrony using gated myocardial perfusion SPECT (MPS) may be an effective tool. The aim of this study was to evaluate global and regional gated MPS dyssynchrony measurements by comparing parameters obtained from patients with a low likelihood (LLk) of conduction abnormalities and coronary artery disease and patients with left bundle branch block (LBBB).

METHODS

A total of 86 consecutive patients with LLk and 72 consecutive patients with LBBB, all without prior myocardial infarction or sternotomy, were studied using gated MPS. Global (histogram SD [sigma], bandwidth [beta], and entropy [epsilon]) and regional (wall- and segment-based differences of means [Deltamicro(W) and Deltamicro(S), respectively] or modes [DeltaM(W) and DeltaM(S), respectively]) dyssynchrony measures were calculated by Fourier harmonic phase-angle analysis of local myocardial count variations over the cardiac cycle for each patient, and then unpaired t tests were used to determine which parameters were sex-specific and how well they discriminated between the LLk and LBBB populations. Receiver-operating-characteristic analysis was also performed to calculate the area under the curve (AUC), sensitivity (Ss), specificity (Sp), and optimal threshold (Th).

RESULTS

Global parameters were found to be sex-specific, whereas regional differences were sex-independent. All parameters studied showed statistically significant differences between the groups (all global, P < 0.05; all regional, P < 0.0001). Receiver-operating-characteristic analysis yielded higher AUC, Ss, and Sp for epsilon and regional parameters (epsilon: AUC = 0.95/0.96, Ss = 94%/88%, Sp = 89%/91%, and Th = 53.9%/60.6% for women/men; Deltamicro(W): AUC = 0.93, Ss = 88%, Sp = 86%, and Th = 10.5 degrees ; Deltamicro(S): AUC = 0.94, Ss = 90%, Sp = 94%, and Th = 9.2 degrees ; DeltaM(W): AUC = 0.95, Ss = 90%, Sp = 94%, and Th = 15 degrees ; and DeltaM(S): AUC = 0.95, Ss = 88%, Sp = 90%, and Th = 10.5 degrees ) than for global parameters (sigma: AUC = 0.75/0.67, Ss = 81%/66%, Sp = 63%/64%, and Th = 16.5 degrees /22.2 degrees for women/men; beta: AUC = 0.80/0.72, Ss = 71%/71%, Sp = 79%/64%, and Th = 69 degrees /81 degrees for women/men).

CONCLUSION

The computed parameters all discriminate effectively between LLk and LBBB populations. Measurements that are less dependent on the shape of the phase-angle distribution histogram provided higher sensitivity and specificity for this purpose. Further study is needed to evaluate these parameters for the purpose of predicting response to CRT.

Longitudinal strain delay index by speckle tracking imaging: a new marker of response to cardiac resynchronization therapy

BACKGROUND

In heart failure patients with left ventricular dyssynchrony, contractility in delayed segments does not fully contribute to end-systolic function. We quantified this reserve of contraction related to mechanical dyssynchrony to predict response to cardiac resynchronization therapy by the strain delay index, which was defined as the sum of the difference between peak and end-systolic strain across 16 segments.

METHODS AND RESULTS

In 100 heart failure patients (ejection fraction=26+/-9%, QRS=154+/-29 ms, 94% in New York Heart Association class III), we studied left ventricular dyssynchrony before cardiac resynchronization therapy by the strain delay index using longitudinal strain by 2D speckle tracking and by the SD of time to peak myocardial velocity in 12 segments. The optimal cutoff value of the strain delay index to predict response to cardiac resynchronization therapy was determined in a retrospective group (n=65) and then confirmed in a validation group (n=35). Left ventricular end-systolic volume reduction at 3 months >15% (responder) occurred in 64 of 100 patients. In the retrospective group, the strain delay index but not the SD of time to peak myocardial velocity was greater in responders (n=42/65) than nonresponders (35+/-8% versus 19+/-7%, P<0.0001), and the optimal cutoff value to identify response to cardiac resynchronization therapy was 25%. In the validation group, strain delay index > or =25% identified 82% (18/22) of responders and 92% (12/13) of nonresponders. Among the entire population (n=100), strain delay index correlated with reverse remodeling in both the ischemic (r=-0.68, P<0.0001) and nonischemic (r=-0.68, P<0.0001) population.

CONCLUSIONS

Use of the strain delay index with longitudinal strain by speckle tracking has a strong predictive value for predicting response to cardiac resynchronization therapy in both ischemic and nonischemic patients.