Mechanism of Abnormal Septal Motion in Left Bundle Branch Block

Predictive value of apical rocking and septal flash for subclinical left ventricular systolic dysfunction in complete left bundle branch block patients with normal left ventricular ejection fraction

BACKGROUND

This study aimed to evaluate the effects of apical rocking(ApRock) and septal flash(SF) on left ventricular function in complete left bundle branch block(CLBBB) patients with normal left ventricular ejection fraction(LVEF), with the goal of improving risk stratification and clinical decision-making for these patients.

METHODS

Seventy-five CLBBB patients with normal LVEF, and 30 age- and sex-matched controls were enrolled in the study. Three independent physicians visually assessed the presence of ApRock and SF and left ventricular global longitudinal strain(LVGLS) and the standard deviation of time-to-peak strain in 18 segments(Ts-SD) were evaluated using two-dimensional speckle-tracking echocardiography.

RESULTS

CLBBB patients with normal LVEF had significantly decreased LV function and synchrony as evidenced by LVGLS and Ts-SD, and CLBBB patients with either ApRock or SF had lower LVGLS than those without ApRock or SF. LVGLS were further decreased and Ts-SD was further increased in CLBBB patients with both ApRock and SF (P < 0.001). Logistic regression analysis revealed that both ApRock (OR, 4.13; P = 0.04) and SF (OR, 4.12; P = 0.03) were independently associated with LVGLS>-20 %. Combination of ApRock and SF showed the highest area under the curve for identifying LVGLS>-20 %. Furthermore, combination of ApRock and SF improved reclassification compared to ApRock alone.

CONCLUSION

CLBBB patients with normal LVEF showed impaired left ventricular systolic function. The presence of both ApRock and SF was a stronger indicator of subclinical left ventricular impairment compared to either one alone, suggesting that increased attention should be paid to CLBBB patients with normal LVEF, particularly those with both ApRock and SF.

Parameter subset reduction for imaging-based digital twin generation of patients with left ventricular mechanical discoordination

BACKGROUND

Integration of a patient's non-invasive imaging data in a digital twin (DT) of the heart can provide valuable insight into the myocardial disease substrates underlying left ventricular (LV) mechanical discoordination. However, when generating a DT, model parameters should be identifiable to obtain robust parameter estimations. In this study, we used the CircAdapt model of the human heart and circulation to find a subset of parameters which were identifiable from LV cavity volume and regional strain measurements of patients with different substrates of left bundle branch block (LBBB) and myocardial infarction (MI). To this end, we included seven patients with heart failure with reduced ejection fraction (HFrEF) and LBBB (study ID: 2018-0863, registration date: 2019-10-07), of which four were non-ischemic (LBBB-only) and three had previous MI (LBBB-MI), and six narrow QRS patients with MI (MI-only) (study ID: NL45241.041.13, registration date: 2013-11-12). Morris screening method (MSM) was applied first to find parameters which were important for LV volume, regional strain, and strain rate indices. Second, this parameter subset was iteratively reduced based on parameter identifiability and reproducibility. Parameter identifiability was based on the diaphony calculated from quasi-Monte Carlo simulations and reproducibility was based on the intraclass correlation coefficient ( ICC ) obtained from repeated parameter estimation using dynamic multi-swarm particle swarm optimization. Goodness-of-fit was defined as the mean squared error (χ 2 ) of LV myocardial strain, strain rate, and cavity volume.

RESULTS

A subset of 270 parameters remained after MSM which produced high-quality DTs of all patients (χ 2  < 1.6), but minimum parameter reproducibility was poor (ICC min  = 0.01). Iterative reduction yielded a reproducible (ICC min  = 0.83) subset of 75 parameters, including cardiac output, global LV activation duration, regional mechanical activation delay, and regional LV myocardial constitutive properties. This reduced subset produced patient-resembling DTs (χ 2  < 2.2), while septal-to-lateral wall workload imbalance was higher for the LBBB-only DTs than for the MI-only DTs (p < 0.05).

CONCLUSIONS

By applying sensitivity and identifiability analysis, we successfully determined a parameter subset of the CircAdapt model which can be used to generate imaging-based DTs of patients with LV mechanical discoordination. Parameters were reproducibly estimated using particle swarm optimization, and derived LV myocardial work distribution was representative for the patient's underlying disease substrate. This DT technology enables patient-specific substrate characterization and can potentially be used to support clinical decision making.

Understanding the Application of Mechanical Dyssynchrony in Patients with Heart Failure Considered for CRT

Over the past two decades of CRT use, the failure rate has remained around 30-35%, despite several updates in the guidelines based on the understanding from multiple trials. This review article summarizes the role of mechanical dyssynchrony in the selection of heart failure patients for cardiac resynchronization therapy. Understanding the application of mechanical dyssynchrony has also evolved during these past two decades. There is no role of lone mechanical dyssynchrony in the patient selection for CRT. However, mechanical dyssynchrony can complement the electrocardiogram and clinical criteria and improve patient selection by reducing the failure rate. An oversimplified approach to mechanical dyssynchrony assessment, such as just estimating time-to-peak delays between segments, should not be used. Instead, methods that can identify the underlying pathophysiology of HF and are representative of a substrate to CRT should be applied.

Acute changes in cardiac dimensions, function, and longitudinal mechanics in healthy individuals with and without high-altitude induced pulmonary hypertension at 4559 m

BACKGROUND

High-altitude pulmonary hypertension (HAPH) has a prevalence of approximately 10%. Changes in cardiac morphology and function at high altitude, compared to a population that does not develop HAPH are scarce.

METHODS

Four hundred twenty-one subjects were screened in a hypoxic chamber inspiring a FiO2  = 12% for 2 h. In 33 subjects an exaggerated increase in systolic pulmonary artery pressure (sPAP) could be confirmed in two independent measurements. Twenty nine of these, and further 24 matched subjects without sPAP increase were examined at 4559 m by Doppler echocardiography including global longitudinal strain (GLS).

RESULTS

SPAP increase was higher in HAPH subjects (∆ = 10.2 vs. ∆ = 32.0 mm Hg, p < .001). LV eccentricity index (∆ = .15 vs. ∆ = .31, p = .009) increased more in HAPH. D-shaped LV (0 [0%] vs. 30 [93.8%], p = .00001) could be observed only in the HAPH group, and only in those with a sPAP ≥50 mm Hg. LV-EF (∆ = 4.5 vs. ∆ = 6.7%, p = .24) increased in both groups. LV-GLS (∆ = 1.2 vs. ∆ = 1.1 -%, p = .60) increased slightly. RV end-diastolic (∆ = 2.20 vs. ∆ = 2.7 cm2 , p = .36) and end-systolic area (∆ = 2.1 vs. ∆ = 2.7 cm2 , p = .39), as well as RA end-systolic area index (∆ = -.9 vs. ∆ = .3 cm2 /m2 , p = .01) increased, RV-FAC (∆ = -2.9 vs. ∆ = -4.7%, p = .43) decreased, this was more pronounced in HAPH, RV-GLS (∆ = 1.6 vs. ∆ = -.7 -%, p = .17) showed marginal changes.

CONCLUSIONS

LV and LA dimensions decrease and left ventricular function increases at high-altitude in subjects with and without HAPH. RV and RA dimensions increase, and RV longitudinal strain increases or remains unchanged in subjects with HAPH. Changes are negligible in those without HAPH.

Virtual pacing of a patient's digital twin to predict left ventricular reverse remodelling after cardiac resynchronization therapy

AIMS

Identifying heart failure (HF) patients who will benefit from cardiac resynchronization therapy (CRT) remains challenging. We evaluated whether virtual pacing in a digital twin (DT) of the patient's heart could be used to predict the degree of left ventricular (LV) reverse remodelling post-CRT.

METHODS AND RESULTS

Forty-five HF patients with wide QRS complex (≥130 ms) and reduced LV ejection fraction (≤35%) receiving CRT were retrospectively enrolled. Echocardiography was performed before (baseline) and 6 months after CRT implantation to obtain LV volumes and 18-segment longitudinal strain. A previously developed algorithm was used to generate 45 DTs by personalizing the CircAdapt model to each patient's baseline measurements. From each DT, baseline septal-to-lateral myocardial work difference (MWLW-S,DT) and maximum rate of LV systolic pressure rise (dP/dtmax,DT) were derived. Biventricular pacing was then simulated using patient-specific atrioventricular delay and lead location. Virtual pacing-induced changes ΔMWLW-S,DT and ΔdP/dtmax,DT were correlated with real-world LV end-systolic volume change at 6-month follow-up (ΔLVESV). The DT's baseline MWLW-S,DT and virtual pacing-induced ΔMWLW-S,DT were both significantly associated with the real patient's reverse remodelling ΔLVESV (r = -0.60, P < 0.001 and r = 0.62, P < 0.001, respectively), while correlation between ΔdP/dtmax,DT and ΔLVESV was considerably weaker (r = -0.34, P = 0.02).

CONCLUSION

Our results suggest that the reduction of septal-to-lateral work imbalance by virtual pacing in the DT can predict real-world post-CRT LV reverse remodelling. This DT approach could prove to be an additional tool in selecting HF patients for CRT and has the potential to provide valuable insights in optimization of CRT delivery.

Imaging in patients with cardiovascular implantable electronic devices: part 1-imaging before and during device implantation. A clinical consensus statement of the European Association of Cardiovascular Imaging (EACVI) and the European Heart Rhythm Association (EHRA) of the ESC

More than 500 000 cardiovascular implantable electronic devices (CIEDs) are implanted in the European Society of Cardiology countries each year. The role of cardiovascular imaging in patients being considered for CIED is distinctly different from imaging in CIED recipients. In the former group, imaging can help identify specific or potentially reversible causes of heart block, the underlying tissue characteristics associated with malignant arrhythmias, and the mechanical consequences of conduction delays and can also aid challenging lead placements. On the other hand, cardiovascular imaging is required in CIED recipients for standard indications and to assess the response to device implantation, to diagnose immediate and delayed complications after implantation, and to guide device optimization. The present clinical consensus statement (Part 1) from the European Association of Cardiovascular Imaging, in collaboration with the European Heart Rhythm Association, provides comprehensive, up-to-date, and evidence-based guidance to cardiologists, cardiac imagers, and pacing specialists regarding the use of imaging in patients undergoing implantation of conventional pacemakers, cardioverter defibrillators, and resynchronization therapy devices. The document summarizes the existing evidence regarding the use of imaging in patient selection and during the implantation procedure and also underlines gaps in evidence in the field. The role of imaging after CIED implantation is discussed in the second document (Part 2).

Echocardiographic Patterns of Abnormal Septal Motion: Beyond Myocardial Ischemia

Abnormal septal motion (ASM), which often is associated with myocardial ischemia, is also observed in other diseases. Owing to the position of the interventricular septum (IVS) in the heart, its movement not only relies on contractile properties but is also affected by the pressure gradient between the 2 ventricles and by the mode of electrical activation. Echocardiography allows the operator to focus on the motion of the IVS, analyzing its characteristics and thereby gaining information about the possible underlying pathophysiological mechanism. In this review, we focused on the main echocardiographic patterns of ASM that are not related to a failure of contractile properties of the septum (i.e., acute coronary syndrome and cardiomyopathies), showing their pathophysiological mechanisms and underlining their diagnostic usefulness in clinical practice.

Left ventricular dyssynchrony measured by cardiovascular magnetic resonance-feature tracking in anterior ST-elevation myocardial infarction: relationship with microvascular occlusion myocardial damage

Objectives

Cardiovascular magnetic resonance-feature tracking (CMR-FT) enables quantification of myocardial deformation and may be used as an objective measure of myocardial involvement in ST-elevation myocardial infarction (STEMI). We sought to investigate the associations between myocardial dyssynchrony parameters and myocardium damage for STEMI.

Methods

We analyzed 65 patients (45-80 years old) with anterior STEMI after primary percutaneous coronary intervention during 3-7 days [observational (STEMI) group] and 60 healthy volunteers [normal control (NC) group]. Myocardial dyssynchrony parameters were derived, including global and regional strain, radial rebound stretch and displacement, systolic septal time delay, and circumferential stretch.

Results

CMR characteristics, including morphologic parameters such as left ventricular ejection fraction (LVEF) (45.3% ± 8.2%) and myocardium damage in late gadolinium enhancement (LGE) (19.4% ± 4.7% LV), were assessed in the observation group. The global radial strain (GRS) and global longitudinal strain (GLS) substantially decreased in anterior STEMI compared with the NC group (GRS: 19.4% ± 5.1% vs. 24.8% ± 4.0%, P < 0.05; GLS: -10.1% ± 1.7% vs. -13.7% ± 1.0%, P < 0.05). Among 362 infarcted segments, radial and circumferential peak strains of the infarcted zone were the lowest (14.4% ± 3.2% and -10.7% ± 1.6%, respectively). The radial peak displacement of the infarct zone significantly decreased (2.6 ± 0.4 mm) (P < 0.001) and manifested in the circumferential displacement (3.5° ± 0.7°) in the STEMI group (P < 0.01). As microvascular occlusion (MVO) was additionally present, some strain parameters were significantly impaired in LGE+/MVO+ segments (radial strain [RS]: 12.2% ± 2.1%, circumferential strain [CS]: -9.6% ± 0.7%, longitudinal strain [LS]: -6.8% ± 1.0%) compared to LGE+/MVO- (RS: 14.6% ± 3.2%, CS: -10.8% ± 1.8%, LS: -9.2% ± 1.3%) (P < 0.05). When the extent of transmural myocardial infarction is greater than 75%, the parameter of the systolic septal delay (mean, 148 ms) was significantly reduced compared to fewer degrees of infarction (P < 0.01).

Conclusion

In anterior STEMI, the infarcted septum swings in a bimodal mode, and myocardial injury reduces the radial strain contractility. A more than 75% transmural degree was the septal strain-contraction reserve cut-off point.

Mechanical Dyssynchrony Combined with Septal Scarring Reliably Identifies Responders to Cardiac Resynchronization Therapy

Background and aim: The presence of mechanical dyssynchrony on echocardiography is associated with reverse remodelling and decreased mortality after cardiac resynchronization therapy (CRT). Contrarily, myocardial scar reduces the effect of CRT. This study investigated how well a combined assessment of different markers of mechanical dyssynchrony and scarring identifies CRT responders. Methods: In a prospective multicentre study of 170 CRT recipients, septal flash (SF), apical rocking (ApRock), systolic stretch index (SSI), and lateral-to-septal (LW-S) work differences were assessed using echocardiography. Myocardial scarring was quantified using cardiac magnetic resonance imaging (CMR) or excluded based on a coronary angiogram and clinical history. The primary endpoint was a CRT response, defined as a ≥15% reduction in LV end-systolic volume 12 months after implantation. The secondary endpoint was time-to-death. Results: The combined assessment of mechanical dyssynchrony and septal scarring showed AUCs ranging between 0.81 (95%CI: 0.74-0.88) and 0.86 (95%CI: 0.79-0.91) for predicting a CRT response, without significant differences between the markers, but significantly higher than mechanical dyssynchrony alone. QRS morphology, QRS duration, and LV ejection fraction were not superior in their prediction. Predictive power was similar in the subgroups of patients with ischemic cardiomyopathy. The combined assessments significantly predicted all-cause mortality at 44 ± 13 months after CRT with a hazard ratio ranging from 0.28 (95%CI: 0.12-0.67) to 0.20 (95%CI: 0.08-0.49). Conclusions: The combined assessment of mechanical dyssynchrony and septal scarring identified CRT responders with high predictive power. Both visual and quantitative markers were highly feasible and demonstrated similar results. This work demonstrates the value of imaging LV mechanics and scarring in CRT candidates, which can already be achieved in a clinical routine.

The saga of dyssynchrony imaging: Are we getting to the point

Cardiac resynchronisation therapy (CRT) has an established role in the management of patients with heart failure, reduced left ventricular ejection fraction (LVEF &lt; 35%) and widened QRS (&gt;130 msec). Despite the complex pathophysiology of left ventricular (LV) dyssynchrony and the increasing evidence supporting the identification of specific electromechanical substrates that are associated with a higher probability of CRT response, the assessment of LVEF is the only imaging-derived parameter used for the selection of CRT candidates.

This review aims to (1) provide an overview of the evolution of cardiac imaging for the assessment of LV dyssynchrony and its role in the selection of patients undergoing CRT; (2) highlight the main pitfalls and advantages of the application of cardiac imaging for the assessment of LV dyssynchrony; (3) provide some perspectives for clinical application and future research in this field.

Conclusion

the road for a more individualized approach to resynchronization therapy delivery is open and imaging might provide important input beyond the assessment of LVEF.

Dyssynchrony and Response to Cardiac Resynchronization Therapy in Heart Failure Patients With Unfavorable Electrical Characteristics

BACKGROUND

Among heart failure (HF) patients undergoing cardiac resynchronization therapy (CRT), those with unfavorable electrical characteristics (UEC) are less frequently CRT responders.

OBJECTIVES

In this study, the authors sought to evaluate the relationship between preprocedural echocardiographic parameters of electromechanical dyssynchrony (EMD) and outcome following CRT.

METHODS

Among 551 patients receiving CRT, 121 with UEC, defined as atypical left bundle branch, presence of right bundle branch block, or unspecified intraventricular conduction disturbance, were enrolled. Indices of EMD were presence of septal flash, apical rocking, septal deformation patterns, and global wasted work (GWW), determined with the use of speckle-tracking strain echocardiography. Endpoints were response to CRT, defined as a relative decrease in left ventricular end-systolic volume ≥15% at 9-month postoperative follow-up, and all-cause death or HF hospitalization during follow-up.

RESULTS

Among the 121 patients, 68 (56%) were CRT responders. In multivariate analysis, GWW ≥200 mm Hg% (adjusted odds ratio [aOR]: 4.17 [95% CI: 1.33-14.56]; P = 0.0182) and longitudinal strain septal contraction patterns 1 and 2 (aOR: 10.05 [95% CI: 2.82-43.97]; P < 0.001) were associated with CRT response. During a 46-month follow-up (IQR: 42-55 months), survival free from death or HF hospitalization increased with the number of positive criteria (87% for 2, 59% for 1, and 27% for 0). After adjustment for established predictors of outcome in patients receiving CRT, absence of either of the 2 criteria remained associated with a considerable increased risk of death and/or HF hospitalization (adjusted HR: 4.83 [95% CI: 1.84-12.68]; P = 0.001).

CONCLUSIONS

In patients with UEC, echocardiographic assessment of EMD may help to select patients who will derive benefit from CRT.

Clinical and Experimental Evidence for a Strain-Based Classification of Left Bundle Branch Block-Induced Cardiac Remodeling

BACKGROUND

Septal strain patterns measured by echocardiography reflect the severity of left bundle branch block (LBBB)-induced left ventricular (LV) dysfunction. We investigated whether these LBBB strain stages predicted the response to cardiac resynchronization therapy in an observational study and developed a sheep model of LBBB-induced cardiomyopathy.

METHODS

The clinical study enrolled cardiac resynchronization therapy patients who underwent echocardiographic examination with speckle-tracking strain analysis before cardiac resynchronization therapy implant. In an experimental sheep model with pacing-induced dyssynchrony, LV remodeling and strain were assessed at baseline, at 8 and 16 weeks. Septal strain curves were classified into 5 patterns (LBBB-0 to LBBB-4).

RESULTS

The clinical study involved 250 patients (age 65 [58; 72] years; 79% men; 89% LBBB) with a median LV ejection fraction of 25 [21; 30]%. Across the stages, cardiac resynchronization therapy resulted in a gradual volumetric response, ranging from no response in LBBB-0 patients (ΔLV end-systolic volume 0 [-12; 15]%) to super-response in LBBB-4 patients (ΔLV end-systolic volume -44 [-64; -18]%) (P<0.001). LBBB-0 patients had a less favorable long-term outcome compared with those in stage LBBB≥1 (log-rank P=0.003). In 13 sheep, acute right ventricular pacing resulted in LBBB-1 (23%) and LBBB-2 (77%) patterns. Over the course of 8-16 weeks, continued pacing resulted in progressive LBBB-induced dysfunction, coincident with a transition to advanced strain patterns (92% LBBB-2 and 8% LBBB-3 at week 8; 75% LBBB-3 and 25% LBBB-4 at week 16) (P=0.023).

CONCLUSIONS

The strain-based LBBB classification reflects a pathophysiological continuum of LBBB-induced remodeling over time and is associated with the extent of reverse remodeling in observational cardiac resynchronization therapy-eligible patients.

Determinants of the time-to-peak left ventricular dP/dt (Td) and QRS duration with different fusion strategies in cardiac resynchronization therapy

Background

Cardiac resynchronization therapy (CRT) is helpful in selected patients; however, responder rates rarely exceed 70%. Optimization of CRT may therefore benefit a large number of patients. Time-to-peak dP/dt (Td) is a novel marker of myocardial synergy that reflects the degree of myocardial dyssynchrony with the potential to guide and optimize treatment with CRT. Optimal electrical activation is a prerequisite for CRT to be effective. Electrical activation can be altered by changing the electrical wave-front fusion resulting from pacing to optimize resynchronization. We designed this study to understand the acute effects of different electrical wave-front fusion strategies and LV pre-/postexcitation on Td and QRS duration (QRSd). A better understanding of measuring and optimizing resynchronization can help improve the benefits of CRT.

Methods

Td and QRSd were measured in 19 patients undergoing a CRT implantation. Two biventricular pacing groups were compared: pacing the left ventricle (LV) with fusion with intrinsic right ventricular activation (FUSION group) and pacing the LV and right ventricle (RV) at short atrioventricular delay (STANDARD group) to avoid fusion with intrinsic RV activation. A quadripolar LV lead enabled pacing from widely separated electrodes; distal (DIST), proximal (PROX) and both electrodes combined (multipoint pacing, MPP). The LV was stimulated relative in time to RV activation (either RV pace-onset or QRS-onset), with the LV stimulated prior to (PRE), simultaneous with (SIM) or after (POST) RV activation. In addition, we analyzed the interactions of the two groups (FUSION/STANDARD) with three different electrode configurations (DIST, PROX, MPP), each paced with three different degrees of LV pre-/postexcitation (PRE, SIM, POST) in a statistical model.

Results

We found that FUSION provided shorter Td and QRSd than STANDARD, MPP provided shorter Td and QRSd than DIST and PROX, and SIM provided both the shortest QRSd and Td compared to PRE and POST. The interaction analysis revealed that pacing MPP with fusion with intrinsic RV activation simultaneous with the onset of the QRS complex (MPP^*FUSION^*SIM) shortened QRSd and Td the most compared to all other modes and configurations. The difference in QRSd and Td from their respective references were significantly correlated (β = 1, R = 0.9, p < 0.01).

Conclusion

Pacing modes and electrode configurations designed to optimize electrical wave-front fusion (intrinsic RV activation, LV multipoint pacing and simultaneous RV and LV activation) shorten QRSd and Td the most. As demonstrated in this study, electrical and mechanical measures of resynchronization are highly correlated. Therefore, Td can potentially serve as a marker for CRT optimization.

Automatic Detection of Aortic Valve Events Using Deep Neural Networks on Cardiac Signals From Epicardially Placed Accelerometer

BACKGROUND

Miniaturized accelerometers incorporated in pacing leads attached to the myocardium, are used to monitor cardiac function. For this purpose functional indices must be extracted from the acceleration signal. A method that automatically detects time of aortic valve opening (AVO) and aortic valve closure (AVC) will be helpful for such extraction. We tested if deep learning can be used to detect these valve events from epicardially attached accelerometers, using high fidelity pressure measurements to establish ground truth for these valve events.

METHOD

A deep neural network consisting of a CNN, an RNN, and a multi-head attention module was trained and tested on 130 recordings from 19 canines and 159 recordings from 27 porcines covering different interventions. Due to limited data, nested cross-validation was used to assess the accuracy of the method.

RESULT

The correct detection rates were 98.9% and 97.1% for AVO and AVC in canines and 98.2% and 96.7% in porcines when defining a correct detection as a prediction closer than 40 ms to the ground truth. The incorrect detection rates were 0.7% and 2.3% for AVO and AVC in canines and 1.1% and 2.3% in porcines. The mean absolute error between correct detections and their ground truth was 8.4 ms and 7.2 ms for AVO and AVC in canines, and 8.9 ms and 10.1 ms in porcines.

CONCLUSION

Deep neural networks can be used on signals from epicardially attached accelerometers for robust and accurate detection of the opening and closing of the aortic valve.

Tracking Early Systolic Motion for Assessing Acute Response to Cardiac Resynchronization Therapy in Real Time

An abnormal systolic motion is frequently observed in patients with left bundle branch block (LBBB), and it has been proposed as a predictor of response to cardiac resynchronization therapy (CRT). Our goal was to investigate if this motion can be monitored with miniaturized sensors feasible for clinical use to identify response to CRT in real time. Motion sensors were attached to the septum and the left ventricular (LV) lateral wall of eighteen anesthetized dogs. Recordings were performed during baseline, after induction of LBBB, and during biventricular pacing. The abnormal contraction pattern in LBBB was quantified by the septal flash index (SFI) equal to the early systolic shortening of the LV septal-to-lateral wall diameter divided by the maximum shortening achieved during ejection. In baseline, with normal electrical activation, there was limited early-systolic shortening and SFI was low (9 ± 8%). After induction of LBBB, this shortening and the SFI significantly increased (88 ± 34%, p < 0.001). Subsequently, CRT reduced it approximately back to baseline values (13 ± 13%, p < 0.001 vs. LBBB). The study showed the feasibility of using miniaturized sensors for continuous monitoring of the abnormal systolic motion of the LV in LBBB and how such sensors can be used to assess response to pacing in real time to guide CRT implantation.

Desynchronization Strain Patterns and Contractility in Left Bundle Branch Block through Computer Model Simulation

Left bundle branch block (LBBB) is associated with specific septal-to-lateral wall activation patterns which are strongly influenced by the intrinsic left ventricular (LV) contractility and myocardial scar localization. The objective of this study was to propose a computational-model-based interpretation of the different patterns of LV contraction observed in the case of LBBB and preserved contractility or myocardial scarring. Two-dimensional transthoracic echocardiography was used to obtain LV volumes and deformation patterns in three patients with LBBB: (1) a patient with non-ischemic dilated cardiomyopathy, (2) a patient with antero-septal myocardial scar, and (3) a patient with lateral myocardial scar. Scar was confirmed by the distribution of late gadolinium enhancement with cardiac magnetic resonance imaging (cMRI). Model parameters were evaluated manually to reproduce patient-derived data such as strain curves obtained from echocardiographic apical views. The model was able to reproduce the specific strain patterns observed in patients. A typical septal flash with pre-ejection shortening, rebound stretch, and delayed lateral wall activation was observed in the case of non-ischemic cardiomyopathy. In the case of lateral scar, the contractility of the lateral wall was significantly impaired and septal flash was absent. In the case of septal scar, septal flash and rebound stretch were also present as previously described in the literature. Interestingly, the model was also able to simulate the specific contractile properties of the myocardium, providing an excellent localization of LV scar in ischemic patients. The model was able to simulate the electromechanical delay and specific contractility patterns observed in patients with LBBB of ischemic and non-ischemic etiology. With further improvement and validation, this technique might be a useful tool for the diagnosis and treatment planning of heart failure patients needing CRT.

A rapid electromechanical model to predict reverse remodeling following cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an effective therapy for patients who suffer from heart failure and ventricular dyssynchrony such as left bundle branch block (LBBB). When it works, it reverses adverse left ventricular (LV) remodeling and the progression of heart failure. However, CRT response rate is currently as low as 50-65%. In theory, CRT outcome could be improved by allowing clinicians to tailor the therapy through patient-specific lead locations, timing, and/or pacing protocol. However, this also presents a dilemma: there are far too many possible strategies to test during the implantation surgery. Computational models could address this dilemma by predicting remodeling outcomes for each patient before the surgery takes place. Therefore, the goal of this study was to develop a rapid computational model to predict reverse LV remodeling following CRT. We adapted our recently developed computational model of LV remodeling to simulate the mechanics of ventricular dyssynchrony and added a rapid electrical model to predict electrical activation timing. The model was calibrated to quantitatively match changes in hemodynamics and global and local LV wall mass from a canine study of LBBB and CRT. The calibrated model was used to investigate the influence of LV lead location and ischemia on CRT remodeling outcome. Our model results suggest that remodeling outcome varies with both lead location and ischemia location, and does not always correlate with short-term improvement in QRS duration. The results and time frame required to customize and run this model suggest promise for this approach in a clinical setting.

To what extent are perfusion defects seen by myocardial perfusion SPECT in patients with left bundle branch block related to myocardial infarction, ECG characteristics, and myocardial wall motion?

INTRODUCTION

We investigated if uptake pattern on myocardial perfusion SPECT (MPS) in patients with left bundle branch block (LBBB) is related to myocardial fibrosis, myocardial wall motion, and electrocardiography (ECG) characteristics.

METHODS

Twenty-three patients (9 women) with LBBB, examined with MPS and cardiac magnetic resonance (CMR), were included. Tracer uptake on MPS was classified by visual interpretation as typical LBBB pattern (Defect+, n = 13) or not (Defect-, n = 10) and quantitatively. CMR images were evaluated for wall thickness and for myocardial wall motion both by visual assessment and by regional myocardial radial strain from feature tracking, and for presence and location of myocardial fibrosis. ECGs were analyzed regarding QRS duration and the presence of strict criteria for LBBB.

RESULTS

Wall thickness was slightly lower in the septum compared to the lateral wall in Defect+ patients (5.6 ± 1.1 vs 6.0 ± 1.3 mm, P = 0.03) but not in Defect- patients (5.6 ± 1.0 vs 5.6 ± 0.9 mm, P = 0.84). Defect+ patients showed a larger proportion of dyskinetic segments in the septum and hyperkinetic segments in the lateral wall compared to Defect- patients (P = 0.006 and P = 0.004, respectively). Decreased myocardial radial strain was associated with decreased tracer uptake by MPS (R = 0.37, P < 0.001). Areas of fibrosis did not match areas with uptake defect on MPS. No differences in ECG variables were seen.

CONCLUSION

The heterogeneous regional tracer uptake in some patients with LBBB is related to underlying regional myocardial dyskinesia, wall thickening, and wall thickness rather than stress-induced ischemia, myocardial fibrosis, or specific ECG characteristics.

Shortening of time-to-peak left ventricular pressure rise (Td) in cardiac resynchronization therapy

Aims

We tested the hypothesis that shortening of time‐to‐peak left ventricular pressure rise (Td) reflect resynchronization in an animal model and that Td measured in patients will be helpful to identify long‐term volumetric responders [end‐systolic volume (ESV) decrease >15%] in cardiac resynchronization therapy (CRT).

Methods

Td was analysed in an animal study (n = 12) of left bundle‐branch block (LBBB) with extensive instrumentation to detect left ventricular myocardial deformation, electrical activation, and pressures during pacing. The sum of electrical delays from the onset of pacing to four intracardiac electrodes formed a synchronicity index (SI). Pacing was performed at baseline, with LBBB, right and left ventricular pacing and finally with biventricular pacing (BIVP). We then studied Td at baseline and with BIVP in a clinical observational study in 45 patients during the implantation of CRT and followed up for up to 88 months.

Results

We found a strong relationship between Td and SI in the animals (R = 0.84, P < 0.01). Td and SI increased from narrow QRS at baseline (Td = 95 ± 2 ms, SI = 141 ± 8 ms) to LBBB (Td = 125 ± 2 ms, SI = 247 ± 9 ms, P < 0.01), and shortened with biventricular pacing (BIVP) (Td = 113 ± 2 ms and SI = 192 ± 7 ms, P < 0.01). Prolongation of Td was associated with more wasted deformation during the preejection period (R = 0.77, P < 0.01). Six patients increased ESV by 2.5 ± 18%, while 37 responders (85%) had a mean ESV decrease of 40 ± 15% after more than 6 months of follow‐up. Responders presented with a higher Td at baseline than non‐responders (163 ± 26 ms vs. 121 ± 19 ms, P < 0.01). Td decreased to 156 ± 16 ms (P = 0.02) with CRT in responders, while in non‐responders, Td increased to 148 ± 21 ms (P < 0.01). A decrease in Td with BIVP to values similar or below what was found at baseline accurately identified responders to therapy (AUC 0.98, P < 0.01). Td at baseline and change in Td from baseline was linear related to the decrease in ESV at follow‐up. All‐cause mortality was high among six non‐responders (n = 4), while no patients died in the responder group during follow‐up.

Conclusions

Prolongation of Td is associated with cardiac dyssynchrony and more wasted deformation during the preejection period. Shortening of a prolonged Td with CRT in patients accurately identifies volumetric responders to CRT with incremental value on top of current guidelines and practices. Thus, Td carries the potential to become a biomarker to predict long‐term volumetric response in CRT candidates.

The value of septal rebound stretch analysis for the prediction of volumetric response to cardiac resynchronization therapy

AIMS

Patient selection for cardiac resynchronization therapy (CRT) may be enhanced by evaluation of systolic myocardial stretching. We evaluate whether systolic septal rebound stretch (SRSsept) derived from speckle tracking echocardiography is a predictor of reverse remodelling after CRT and whether it holds additive predictive value over the simpler visual dyssynchrony assessment by apical rocking (ApRock).

METHODS AND RESULTS

The association between SRSsept and change in left ventricular end-systolic volume (ΔLVESV) at 6 months of follow-up was assessed in 200 patients. Subsequently, the additive predictive value of SRSsept over the assessment of ApRock was evaluated in patients with and without left bundle branch block (LBBB) according to strict criteria. SRSsept was independently associated with ΔLVESV (β 0.221, P = 0.002) after correction for sex, age, ischaemic cardiomyopathy, QRS morphology and duration, and ApRock. A high SRSsept (≥optimal cut-off value 2.4) also coincided with more volumetric responders (ΔLVESV ≥ -15%) than low SRSsept in the entire cohort (70.0% and 56.4%), in patients with strict LBBB (83.3% vs. 56.7%, P = 0.024), and non-LBBB (70.7% vs. 46.3%, P = 0.004). Moreover, in non-LBBB patients, SRSsept held additional predictive information over the assessment of ApRock alone since patients that showed ApRock and high SRSsept were more often volumetric responder than those with ApRock but low SRSsept (82.8% vs. 47.4%, P = 0.001).

CONCLUSION

SRSsept is strongly associated with CRT-induced reduction in left ventricular end-systolic volume and holds additive prognostic information over QRS morphology and ApRock. Our data suggest that CRT patient selection may be improved by assessment of SRSsept, especially in the important subgroup without strict LBBB.

CLINICAL TRIAL REGISTRATION

The MARC study was registered at clinicaltrials.gov: NCT01519908.

Clinical Significance of Global Wasted Work in Patients with Heart Failure Receiving Cardiac Resynchronization Therapy

BACKGROUND

The relationship between myocardial work assessment using pressure-strain loops by echocardiography before cardiac resynchronization therapy (CRT) and response to CRT has been recently revealed. Among myocardial work parameters, the impact of left ventricular myocardial global wasted work (GWW) on response to CRT and outcome following CRT has been seldom studied. Hence, the authors evaluated the relationship between preprocedural GWW and outcome in a large prospective cohort of patients with heart failure (HF) and reduced ejection fraction receiving CRT.

METHODS

The study included 249 patients with HF. Myocardial work indices including GWW were calculated using speckle-tracking strain two-dimensional echocardiography using pressure-strain loops. End points of the study were (1) response to CRT, defined as left ventricular reverse remodeling and/or absence of hospitalization for HF, and (2) all-cause death during follow-up.

RESULTS

Median follow-up duration was 48 months (interquartile range, 43-54 months). Median preoperative GWW was 281 mm Hg% (interquartile range, 184-388 mm Hg%). Preoperative GWW was associated with CRT response (area under the curve, 0.74; P < .0001), and a 200 mm Hg% threshold discriminated CRT nonresponders from responders with 85% specificity and 50% sensitivity, even after adjustment for known predictors of CRT response (adjusted odds ratio, 4.03; 95% CI, 1.91-8.68; P < .001). After adjustment for established predictors of outcome in patients with HF with reduced ejection fraction receiving CRT, GWW < 200 mm Hg% remained associated with a relative increased risk for all-cause death compared with GWW ≥ 200 mm Hg% (adjusted hazard ratio, 2.0; 95% CI, 1.1-3.9; P = .0245). Adding GWW to a baseline model including known predictors of outcome in CRT resulted in an improvement of this model (χ² to improve 4.85, P = .028). The relationship between GWW and CRT response and outcome was stronger in terms of size effect and statistical significance than for other myocardial work indices.

CONCLUSIONS

Low preoperative GWW (<200 mm Hg%) is associated with absence of CRT response in CRT candidates and with a relative increased risk for all-cause death. GWW appears to be a promising parameter to improve selection for CRT of patients with HF with reduced ejection fraction.

Lateral Wall Dysfunction Signals Onset of Progressive Heart Failure in Left Bundle Branch Block

OBJECTIVES

This study sought to investigate if contractile asymmetry between septum and left ventricular (LV) lateral wall drives heart failure development in patients with left bundle branch block (LBBB) and whether the presence of lateral wall dysfunction affects potential for recovery of LV function with cardiac resynchronization therapy (CRT).

BACKGROUND

LBBB may induce or aggravate heart failure. Understanding the underlying mechanisms is important to optimize timing of CRT.

METHODS

In 76 nonischemic patients with LBBB and 11 controls, we measured strain using speckle-tracking echocardiography and regional work using pressure-strain analysis. Patients with LBBB were stratified according to LV ejection fraction (EF) ≥50% (EF_preserved), 36% to 49% (EF_mid), and ≤35% (EF_low). Sixty-four patients underwent CRT and were re-examined after 6 months.

RESULTS

Septal work was successively reduced from controls, through EF_preserved, EF_mid, and EF_low (all p < 0.005), and showed a strong correlation to left ventricular ejection fraction (LVEF; r = 0.84; p < 0.005). In contrast, LV lateral wall work was numerically increased in EF_preserved and EF_mid versus controls, and did not significantly correlate with LVEF in these groups. In EF_low, however, LV lateral wall work was substantially reduced (p < 0.005). There was a moderate overall correlation between LV lateral wall work and LVEF (r = 0.58; p < 0.005). In CRT recipients, LVEF was normalized (≥50%) in 54% of patients with preserved LV lateral wall work, but only in 13% of patients with reduced LV lateral wall work (p < 0.005).

CONCLUSIONS

In early stages, LBBB-induced heart failure is associated with impaired septal function but preserved lateral wall function. The advent of LV lateral wall dysfunction may be an optimal time-point for CRT.

A Strain-Based Staging Classification of Left Bundle Branch Block-Induced Cardiac Remodeling

OBJECTIVES

This study speculated that longitudinal strain curves in left bundle branch block (LBBB) could be shaped by the degree of LBBB-induced cardiac remodeling.

BACKGROUND

LBBB independently affects left ventricular (LV) structure and function, but large individual variability may exist in LBBB-induced adverse remodeling.

METHODS

Consecutive patients with LBBB with septal flash (LBBB-SF) underwent thorough echocardiographic assessment, including speckle tracking-based strain analysis. Four major septal longitudinal strain patterns (LBBB-1 through LBBB-4) were discerned and staged on the basis of: 1) correlation analysis with echocardiographic indexes of cardiac remodeling, including the extent of SF; 2) strain pattern analysis in cardiac resynchronization therapy (CRT) super-responders; and 3) strain pattern analysis in patients with acute procedural-induced LBBB.

RESULTS

The study enrolled 237 patients with LBBB-SF (mean age: 67 ± 13 years; 57% men). LBBB-1 was observed in 60 (26%), LBBB-2 in 118 (50%), LBBB-3 in 29 (12%), and LBBB-4 in 26 (11%) patients. Patients at higher LBBB stages had larger end-diastolic volumes, lower LV ejection fractions, longer QRS duration, increased mechanical dyssynchrony, and more prominent SF compared with less advanced stages (p < 0.001 for all). Among CRT super-responders (n = 30; mean age: 63 ± 10 years), an inverse transition from stages LBBB-3 and -4 (pre-implant) to stages LBBB-1 and -2 (pace-off, median follow-up of 66 months [interquartile range: 32 to 78 months]) was observed (p < 0.001). Patients with acute LBBB (n = 27; mean age: 83 ± 5.1 years) only presented with a stage LBBB-1 (72%) or -2 pattern (24%).

CONCLUSIONS

The proposed classification suggests a pathophysiological continuum of LBBB-induced LV remodeling and may be valuable to assess the attribution of LBBB to the extent of LV remodeling and dysfunction.

Segment length in cine (SLICE) strain analysis: a practical approach to estimate potential benefit from cardiac resynchronization therapy

BACKGROUND

Segment length in cine (SLICE) strain analysis on standard cardiovascular magnetic resonance (CMR) cine images was recently validated against gold standard myocardial tagging. The present study aims to explore predictive value of SLICE for cardiac resynchronization therapy (CRT) response.

METHODS AND RESULTS

Fifty-seven patients with heart failure and left bundle branch block (LBBB) were prospectively enrolled in this multi-center study and underwent CMR examination before CRT implantation. Circumferential strains of the septal and lateral wall were measured by SLICE on short-axis cine images. In addition, timing and strain pattern parameters were assessed. After twelve months, CRT response was quantified by the echocardiographic change in left ventricular (LV) end-systolic volume (LVESV). In contrast to timing parameters, strain pattern parameters being systolic rebound stretch of the septum (SRSsep), systolic stretch index (SSIsep-lat), and internal stretch factor (ISFsep-lat) all correlated significantly with LVESV change (R - 0.56; R - 0.53; and R - 0.58, respectively). Of all strain parameters, end-systolic septal strain (ESSsep) showed strongest correlation with LVESV change (R - 0.63). Multivariable analysis showed ESSsep to be independently related to LVESV change together with age and QRSAREA.

CONCLUSION

The practicable SLICE strain technique may help the clinician to estimate potential benefit from CRT by analyzing standard CMR cine images without the need for commercial software. Of all strain parameters, end-systolic septal strain (ESSsep) demonstrates the strongest correlation with reverse remodeling after CRT. This parameter may be of special interest in patients with non-strict LBBB morphology for whom CRT benefit is doubted.

Clinical and prognostic implications of phenomapping in patients with heart failure receiving cardiac resynchronization therapy

BACKGROUND

Despite having an indication for cardiac resynchronization therapy according to current guidelines, patients with heart failure with reduced ejection fraction who receive cardiac resynchronization therapy do not consistently derive benefit from it.

AIM

To determine whether unsupervised clustering analysis (phenomapping) can identify distinct phenogroups of patients with differential outcomes among cardiac resynchronization therapy recipients from routine clinical practice.

METHODS

We used unsupervised hierarchical cluster analysis of phenotypic data after data reduction (55 clinical, biological and echocardiographic variables) to define new phenogroups among 328 patients with heart failure with reduced ejection fraction from routine clinical practice enrolled before cardiac resynchronization therapy. Clinical outcomes and cardiac resynchronization therapy response rate were studied according to phenogroups.

RESULTS

Although all patients met the recommended criteria for cardiac resynchronization therapy implantation, phenomapping analysis classified study participants into four phenogroups that differed distinctively in clinical, biological, electrocardiographic and echocardiographic characteristics and outcomes. Patients from phenogroups 1 and 2 had the most improved outcome in terms of mortality, associated with cardiac resynchronization therapy response rates of 81% and 78%, respectively. In contrast, patients from phenogroups 3 and 4 had cardiac resynchronization therapy response rates of 39% and 59%, respectively, and the worst outcome, with a considerably increased risk of mortality compared with patients from phenogroup 1 (hazard ratio 3.23, 95% confidence interval 1.9-5.5 and hazard ratio 2.49, 95% confidence interval 1.38-4.50, respectively).

CONCLUSIONS

Among patients with heart failure with reduced ejection fraction with an indication for cardiac resynchronization therapy from routine clinical practice, phenomapping identifies subgroups of patients with differential clinical, biological and echocardiographic features strongly linked to divergent outcomes and responses to cardiac resynchronization therapy. This approach may help to identify patients who will derive most benefit from cardiac resynchronization therapy in "individualized" clinical practice.

Automatic detection of valve events by epicardial accelerometer allows estimation of the left ventricular pressure trace and pressure-displacement loop area

Measurements of the left ventricular (LV) pressure trace are rarely performed despite high clinical interest. We estimated the LV pressure trace for an individual heart by scaling the isovolumic, ejection and filling phases of a normalized, averaged LV pressure trace to the time-points of opening and closing of the aortic and mitral valves detected in the individual heart. We developed a signal processing algorithm that automatically detected the time-points of these valve events from the motion signal of a miniaturized accelerometer attached to the heart surface. Furthermore, the pressure trace was used in combination with measured displacement from the accelerometer to calculate the pressure–displacement loop area. The method was tested on data from 34 animals during different interventions. The accuracy of the accelerometer-detected valve events was very good with a median difference of 2 ms compared to valve events defined from hemodynamic reference recordings acquired simultaneously with the accelerometer. The average correlation coefficient between the estimated and measured LV pressure traces was r = 0.98. Finally, the LV pressure–displacement loop areas calculated using the estimated and measured pressure traces showed very good correlation (r = 0.98). Hence, the pressure–displacement loop area can be assessed solely from accelerometer recordings with very good accuracy.

Left ventricle and mitral valve reverse remodeling in response to cardiac resynchronization therapy in nonischemic cardiomyopathy

BACKGROUND

Cardiac resynchronization therapy (CRT) improves left heart geometry and function in nonischemic cardiomyopathy (NICMP). We aimed to detail the effects of CRT on left ventricular (LV) and mitral valve (MV) remodeling using 2-dimensional transthoracic echocardiography.

METHODS

Forty-five consecutive patients with NICMP who underwent CRT implantation between 2009 and 2012, and had pre-CRT and follow-up echocardiograms available, were included. Paired t test, linear and logistic regression, and Kaplan-Meier survival analyses were used for statistical assessment.

RESULTS

The mean age and QRS duration were 60 years and 157 ms, respectively, and 13 (28.9%) were female. At a mean follow-up of 3 years, there were 22 (48.9%) "CRT responders" (≥15% reduction in LV end-systolic volume index [LVESVi]). Significant improvements were observed in LV ejection fraction (26.3% vs 34.3%) and LVESVi (87.7 vs 71.1 mL/m² ), as well as mitral regurgitation vena contracta width, MV tenting height and area, and end-systolic interpapillary muscle distance. Five-year actuarial survival was 87.5%. Multivariate regression analyses revealed the pre-CRT LVESVi (β = 0.52), and MV coaptation length (β = -0.34) and septolateral annular diameter (β = 0.25) as good correlates of follow-up LVESVi. Variables associated with CRT response were pre-CRT MV coaptation length (OR 1.75, 95% CI 1.0-3.1) and posterior leaflet tethering angle (OR 1.07, 95% CI 1.0-1.14), irrespective of baseline QRS morphology and duration (all P < .05).

CONCLUSIONS

Cardiac resynchronization therapy improves LV and MV geometry and function in half of patients with NICMP, which is paralleled by decreased mitral regurgitation severity. The extent of pre-CRT LV remodeling and MV tethering are associated with CRT response.

Imaging predictors of response to cardiac resynchronization therapy: left ventricular work asymmetry by echocardiography and septal viability by cardiac magnetic resonance

AIMS

Left ventricular (LV) failure in left bundle branch block is caused by loss of septal function and compensatory hyperfunction of the LV lateral wall (LW) which stimulates adverse remodelling. This study investigates if septal and LW function measured as myocardial work, alone and combined with assessment of septal viability, identifies responders to cardiac resynchronization therapy (CRT).

METHODS AND RESULTS

In a prospective multicentre study of 200 CRT recipients, myocardial work was measured by pressure-strain analysis and viability by cardiac magnetic resonance (CMR) imaging (n = 125). CRT response was defined as ≥15% reduction in LV end-systolic volume after 6 months. Before CRT, septal work was markedly lower than LW work (P < 0.0001), and the difference was largest in CRT responders (P < 0.001). Work difference between septum and LW predicted CRT response with area under the curve (AUC) 0.77 (95% CI: 0.70-0.84) and was feasible in 98% of patients. In patients undergoing CMR, combining work difference and septal viability significantly increased AUC to 0.88 (95% CI: 0.81-0.95). This was superior to the predictive power of QRS morphology, QRS duration and the echocardiographic parameters septal flash, apical rocking, and systolic stretch index. Accuracy was similar for the subgroup of patients with QRS 120-150 ms as for the entire study group. Both work difference alone and work difference combined with septal viability predicted long-term survival without heart transplantation with hazard ratio 0.36 (95% CI: 0.18-0.74) and 0.21 (95% CI: 0.072-0.61), respectively.

CONCLUSION

Assessment of myocardial work and septal viability identified CRT responders with high accuracy.

Acute redistribution of regional left ventricular work by cardiac resynchronization therapy determines long-term remodelling

Aims 

Investigating the acute impact of cardiac resynchronization therapy (CRT) on regional myocardial work distribution in the left ventricle (LV) and to which extent it is related to long-term reverse remodelling.

Methods and results 

One hundred and thirty heart failure patients, referred for CRT implantation, were recruited in our prospective multicentre study. Regional myocardial work was calculated from non-invasive segmental stress–strain loop area before and immediately after CRT. The magnitude of volumetric reverse remodelling was determined from the change in LV end-systolic volume, 11 ± 2 months after implantation. CRT caused acute redistribution of myocardial work across the LV, with an increase in septal work, and decrease in LV lateral wall work (all P &lt; 0.05). Amongst all LV walls, the acute change in work in the septum and lateral wall of the four-chamber view correlated best and significantly with volumetric reverse remodelling (r = 0.62, P &lt; 0.0001), with largest change seen in patients with most volumetric reverse remodelling. In multivariate linear regression analysis, including conventional parameters, such as pre-implant QRS morphology and duration, LV ejection fraction, ischaemic origin of cardiomyopathy, and the redistribution of work across the septal and lateral walls, the latter appeared as the strongest determinant of volumetric reverse remodelling after CRT (model R2 = 0.414, P &lt; 0.0001).

Conclusion 

The acute redistribution of regional myocardial work between the septal and lateral wall of the LV is an important determinant of reverse remodelling after CRT implantation. Our data suggest that the treatment of the loading imbalance should, therefore, be the main aim of CRT.

Myocardial Efficiency: A Fundamental Physiological Concept on the Verge of Clinical Impact

Myocardial external efficiency is the relation of mechanical energy generated by the left (or right) ventricle to the consumed chemical energy from aerobic metabolism. Efficiency can be calculated invasively, and, more importantly, noninvasively by using positron emission tomography, providing a single parameter by which to judge the adequacy of myocardial metabolism to generated mechanical output. This parameter has been found to be impaired in heart failure of myocardial or valvular etiology, and it changes in a characteristic manner with medical or interventional cardiac therapy. The authors discuss the concept, strengths, and limitations, known applications, and future perspectives of the use of myocardial efficiency.