Identification of Typical Left Bundle Branch Block Contraction by Strain Echocardiography Is Additive to Electrocardiography in Prediction of Long-Term Outcome After Cardiac Resynchronization Therapy

Cardiac Resynchronization Therapy and Conduction System Pacing

Left bundle branch block (LBBB), initially described in the early 20th century, has become increasingly recognized as one of the leading causes of advanced heart failure (HF). In addition to rapidly growing data on guideline-directed medical therapy, cardiac resynchronization therapy (CRT) via transvenous coronary sinus lead has been the gold-standard therapy, but one-third of the indicated patients do not receive the expected benefits. Recently, cardiac conduction system pacing (CSP) was identified as an alternative to traditional CRT strategy, and multiple data have been published during the last few years. This review will discuss the diagnostic criteria of LBBB and its relation to the development of HF and review available data for traditional CRT as well as CSP in depth.

Myocardial Strain Imaging: Theory, Current Practice, and the Future

Myocardial strain imaging by echocardiography or cardiac magnetic resonance (CMR) is a powerful method to diagnose cardiac disease. Strain imaging provides measures of myocardial shortening, thickening, and lengthening and can be applied to any cardiac chamber. Left ventricular (LV) global longitudinal strain by speckle-tracking echocardiography is the most widely used clinical strain parameter. Several CMR-based modalities are available and are ready to be implemented clinically. Clinical applications of strain include global longitudinal strain as a more sensitive method than ejection fraction for diagnosing mild systolic dysfunction. This applies to patients suspected of having heart failure with normal LV ejection fraction, to early systolic dysfunction in valvular disease, and when monitoring myocardial function during cancer chemotherapy. Segmental LV strain maps provide diagnostic clues in specific cardiomyopathies, when evaluating LV dyssynchrony and ischemic dysfunction. Strain imaging is a promising modality to quantify right ventricular function. Left atrial strain may be used to evaluate LV diastolic function and filling pressure.

Development of right ventricular electromechanical dyssynchrony following surgical repair of tetralogy of Fallot in infants

Background

In adolescents and adults with tetralogy of Fallot (TOF), right ventricle (RV) electromechanical dyssynchrony (EMD) due to right bundle branch block (RBBB) is associated with reduced exercise capacity and RV dysfunction. While the development of RBBB following surgical repair of tetralogy of Fallot (rTOF) is a frequent sequela, it is not known whether EMD is present in every patient immediately following rTOF. The specific timing of the onset of RBBB following rTOF therefore provides an opportunity to assess whether acute RBBB is associated with the simultaneous acquisition of EMD.

Methods

Transthoracic echocardiography with speckle tracking analysis for RV global longitudinal strain (GLS) and 12-lead ECG were performed prospectively on 20 infants following rTOF. Three apical RV views were obtained using analogous imaging planes to the standard LV views to provide a comprehensive evaluation. Regional RV GLS patterns were categorized as synchronous, EMD, or indeterminate. EMD was defined as an early-terminated septal contraction opposed by early stretch and post-systolic peak contraction in the activation delayed RV free wall. An indeterminate pattern was defined as a lack of fully synchronous contraction of all segments but not meeting criteria for EMD. Pre-rTOF echocardiograms and ECGs were analyzed to confirm the presence of synchronous contraction and a normal QRS pattern and duration prior to surgery.

Results

Twenty TOF infants (median age 87 days; 8 days from surgery to post-rTOF evaluation) demonstrated QRSd prolongation following rTOF (pre-rTOF 58 ± 9 ms; post-rTOF 97 ± 14 ms; p < 0.001) with new RBBB morphology in all but one patient. All pre-rTOF RV strain patterns were synchronous. Post-rTOF RV strain analysis showed EMD in 25% (5/20) and an indeterminate pattern in 40% (8/20) with the remaining 35% (7/20) maintaining a synchronous pattern, including the patient without RBBB. The EMD group had the lowest RV GLS following repair (p = 0.006).

Discussion

Acquisition of acute QRS prolongation in a RBBB pattern is near-universal following rTOF but without matched or identical patterns of dyssynchrony, suggesting that variations in the time from electrical to electromechanical dyssynchrony potentially caused by differences in right bundle branch anatomy and injury may be relevant to electromechanical outcomes.

Enhanced Extraction of Activation Time and Contractility From Myocardial Strain Data Using Parameter Space Features and Computational Simulations

A computational model enables the extraction of two critical myocardial tissue properties: activation time (AT) and contractility (Con) from recorded cardiac strains. However, interference between these parameters reduces the precision and accuracy of the extraction process. This study investigates whether leveraging features in the parameter space can enhance parameter extraction. We utilized a computational model to simulate sarcomere mechanics, creating a parameter space grid of 41 × 41 AT and Con pairs. Each pair generated a simulated strain pattern, and by scanning the grid, we identified cohorts of similar strain patterns for each simulation. These cohorts were represented as binary images-synthetic fingerprints-where the position and shape of each blob indicated extraction uniqueness. We also generated a measurement fingerprint for a strain pattern from a patient with left bundle branch block and compared it to the synthetic fingerprints to calculate a proximity map based on their similarity. This approach allowed us to extract AT and Con using both the measurement fingerprint and the proximity map, corresponding to simple optimization and enhanced parameter extraction methods, respectively. Each synthetic fingerprint consisted of a single connected blob whose size and shape varied characteristically within the parameter space. The AT values extracted from the measurement fingerprint and the proximity map ranged from -59 to 19 ms and from -16 to 14 ms, respectively, while Con values ranged from 48% to 110% and from 85% to 110%, respectively. This study demonstrates that similarity in simulations leads to an asymmetric distribution of parameter values in the parameter space. By using a proximity map, this distortion is considered, significantly improving the accuracy of parameter extraction.

Longitudinal comparison of dyssynchrony correction and 'strain' improvement by conduction system pacing: LEVEL-AT trial secondary findings

AIMS

Longitudinal dyssynchrony correction and 'strain' improvement by comparable cardiac resynchronization therapy (CRT) techniques is unreported. Our purpose was to compare echocardiographic dyssynchrony correction and 'strain' improvement by conduction system pacing (CSP) vs. biventricular pacing (BiVP) as a marker of contractility improvement during 1-year follow-up.

METHODS AND RESULTS

A treatment-received analysis was performed in patients included in the LEVEL-AT trial (NCT04054895), randomized to CSP or BiVP, and evaluated at baseline (ON and OFF programming) and at 6 and 12 months (n = 69, 32% women). Analysis included intraventricular (septal flash), interventricular (difference between left and right ventricular outflow times), and atrioventricular (diastolic filling time) dyssynchrony and 'strain' parameters [septal rebound, global longitudinal 'strain' (GLS), LBBB pattern, and mechanical dispersion). Baseline left ventricular ejection fraction (LVEF) was 27.5 ± 7%, and LV end-systolic volume (LVESV) was 138 ± 77 mL, without differences between groups. Longitudinal analysis showed LVEF and LVESV improvement (P < 0.001), without between-group differences. At 12-month follow-up, adjusted mean LVEF was 46% with CSP (95% CI 42.2 and 49.3%) vs. 43% with BiVP (95% CI 39.6 and 45.8%), (P = 0.31), and LVESV was 80 mL (95% CI 55.3 and 104.5 mL) vs. 100 mL (95% CI 78.7 and 121.6 mL), respectively (P = 0.66). Longitudinal analysis showed a significant improvement of all dyssynchrony parameters and GLS over time (P < 0.001), without differences between groups. Baseline GLS significantly correlated with LVEF and LVESV at 12-month follow-up.

CONCLUSION

CSP and BiVP provided similar dyssynchrony and 'strain' correction over time. Baseline global longitudinal 'strain' predicted ventricular remodelling at 12-month follow-up.

Left Bundle Branch Block-associated Cardiomyopathy: A New Approach

Left bundle branch block (LBBB) is frequently associated with structural heart disease, and predicts higher rates of morbidity and mortality. In patients with cardiomyopathy (ejection fraction <35%) and LBBB, current guidelines recommend cardiac resynchronisation therapy (CRT) after 3 months of medical therapy. However, studies have suggested that medical therapy alone would be less effective, and the majority of patients would still need CRT at the end of 3 months. Conversely, CRT trials have shown better results and favourable clinical outcomes in patients with LBBB. In the absence of any other known aetiology, LBBB-associated cardiomyopathy represents a potentially reversible form of cardiomyopathy, with the majority of the patients having reverse remodelling after CRT by left bundle branch pacing. This review provides the mechanism, published evidence and role of conduction system pacing for patients with LBBB-associated cardiomyopathy.

Relationship between sex, body size, and cardiac resynchronization therapy benefit: A patient-level meta-analysis of randomized controlled trials

BACKGROUND

Women might benefit more than men from cardiac resynchronization therapy (CRT) and do so at shorter QRS durations.

OBJECTIVE

This meta-analysis was performed to determine whether sex-based differences in CRT effects are better accounted for by height, body surface area (BSA), or left ventricular end-diastolic dimension (LVEDD).

METHODS

We analyzed patient-level data from CRT trials (MIRACLE, MIRACLE ICD, MIRACLE ICD II, REVERSE, RAFT, COMPANION, and MADIT-CRT) using bayesian hierarchical Weibull regression models. Relationships between QRS duration and CRT effects were examined overall and in sex-stratified cohorts; additional analyses indexed QRS duration by height, BSA, or LVEDD. End points were heart failure hospitalization (HFH) or death and all-cause mortality.

RESULTS

Compared with men (n = 5628), women (n = 1439) were shorter (1.62 [interquartile range, 1.57-1.65] m vs 1.75 [1.70-1.80] m; P < .001), with smaller BSAs (1.76 [1.62-1.90] m2 vs 2.02 [1.89-2.16] m2; P < .001). In adjusted sex-stratified analyses, the reduction in HFH or death was greater for women (hazard ratio, 0.54; credible interval, 0.42-0.70) than for men (hazard ratio, 0.77; credible interval, 0.66-0.89; Pinteraction = .009); results were similar for all-cause mortality even after adjustment for height, BSA, and LVEDD. Sex-specific differences were observed only in nonischemic cardiomyopathy. The effect of CRT on HFH or death was observed at a shorter QRS duration for women (126 ms) than for men (145 ms). Indexing QRS duration by height, BSA, or LVEDD attenuated sex-specific QRS duration thresholds for the effects of CRT on HFH or death but not on mortality.

CONCLUSION

Although body size partially explains sex-specific QRS duration thresholds for CRT benefit, it is not associated with the magnitude of CRT benefit. Indexing QRS duration for body size might improve selection of patients for CRT, particularly with a "borderline" QRS duration.

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.

Clinical significance of regional constructive and wasted work in patients receiving cardiac resynchronization therapy

Background

Previous studies have shown that global constructive work (CW) and wasted work (WW) predict response to cardiac resynchronization therapy (CRT). This study evaluated the predictive value of regional CW and WW for reverse remodeling and clinical outcomes after CRT.

Methods

We performed a prospective study involving 134 CRT candidates with left bundle branch block and left ventricular ejection fraction ≤35%. Global and regional CW and WW were calculated using pressure-strain loop analysis. CRT response was defined by reverse remodeling as a reduction of ≥15% in left ventricular end-systolic volume after six months.

Results

At six-month follow-up, 92 (69%) patients responded to CRT. Of the regional CW and WW measures, lateral wall (LW) CW and septal WW were most strongly and significantly correlated with reverse remodeling. At multivariate analysis, LW CW and septal WW were both independent determinants of reverse remodeling. When LW CW and septal WW were included in the model, global CW and WW were not independently associated with reverse remodeling. LW CW and septal WW predicted reverse remodeling with an area under the curve (AUC) of 0.783 (95% CI: 0.700-0.866) and 0.737 (95% CI: 0.644-0.831), respectively. Using both variables increased the AUC to 0.832 (95% CI: 0.755-0.908). Both LW CW ≤878 mmHg% (HR 2.01; 95% CI: 1.07-3.79) and septal WW ≤181 mmHg% (HR 2.60; 95% CI: 1.38-4.90) were significant predictors of combined death and HF hospitalization at two-year follow-up.

Conclusion

LW CW and septal WW before CRT are important determinants of reverse remodeling and clinical outcomes.

Assessment of myocardial strain patterns in patients with left bundle branch block using cardiac magnetic resonance

Recently, a classification with four types of septal longitudinal strain patterns was described using echocardiography, suggesting a pathophysiological continuum of left bundle branch block (LBBB)-induced left ventricle (LV) remodeling. The aim of this study was to assess the feasibility of classifying these strain patterns using cardiovascular magnetic resonance (CMR), and to evaluate their association with LV remodeling and myocardial scar. Single center registry included LBBB patients with septal flash (SF) referred to CMR to assess the cause of LV systolic dysfunction. Semi-automated feature-tracking cardiac resonance (FT-CMR) was used to quantify myocardial strain and detect the four strain patterns. A total of 115 patients were studied (age 66 ± 11 years, 57% men, 28% with ischemic heart disease). In longitudinal strain analysis, 23 patients (20%) were classified in stage LBBB-1, 37 (32.1%) in LBBB-2, 25 (21.7%) in LBBB-3, and 30 (26%) in LBBB-4. Patients at higher stages had more prominent septal flash, higher LV volumes, lower LV ejection fraction, and lower absolute strain values (p < 0.05 for all). Late gadolinium enhancement (LGE) was found in 55% of the patients (n = 63). No differences were found between the strain patterns regarding the presence, distribution or location of LGE. Among patients with LBBB, there was a good association between strain patterns assessed by FT-CMR analysis and the degree of LV remodeling and LV dysfunction. This association seems to be independent from the presence and distribution of LGE.

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.

Multimodality Imaging for Selecting Candidates for CRT: Do We Have a Single Alley to Increase Responders?

Cardiac resynchronization therapy has evolved in recent years to provide a reduction of morbidity and mortality for many patients with heart failure. Its application and optimization is an evolving field and its use requires a multidisciplinary approach for patient and device selection, technical preprocedural planning, and optimization. While echocardiography has always been considered the first line for the evaluation of patients, additional imaging techniques have gained increasing evidence in recent years. Today different details about heart anatomy, function, dissynchrony can be investigated by magnetic resonance, cardiac computed tomography, nuclear imaging, and more, with the aim of obtaining clues to reach a maximal response from the electrical therapy. The purpose of this review is to provide a practical analysis of the single and combined use of different imaging techniques in the preoperative and perioperative phases of cardiac resynchronization therapy, underlining their main advantages, limitations, and information provided.

Efficacy on resynchronization and longitudinal contractile function comparing His-bundle pacing with conventional biventricular pacing: a substudy to the His-alternative study

AIMS

His-bundle pacing has emerged as a novel method to deliver cardiac resynchronization therapy (CRT). However, there are no data comparing conventional biventricular (BiV)-CRT with His-CRT with regard to effects on mechanical dyssynchrony and longitudinal contractile function.

METHODS AND RESULTS

Patients with symptomatic heart failure, left ventricular ejection fraction ≤ 35%, and left bundle branch block (LBBB) by strict ECG criteria were randomized 1:1 to His-CRT or BiV-CRT. Two-dimensional strain echocardiography was performed prior to CRT implantation and at 6 months after implantation. Differences in changes in mechanical dyssynchrony (standard deviation of time-to-peak in 12 midventricular and basal segments) and regional longitudinal strain in the six left ventricular walls were compared between the BiV-CRT and His-CRT groups.In the on-treatment analysis, 31 received BiV-CRT and 19 His-CRT. In both groups, mechanical dyssynchrony was significantly reduced after 6 months [BiV group from 120 ms (±45) to 63 ms (±22), P < 0.001, and His group from 116 ms (±54) to 49 ms (±11), P < 0.001] but no significant differences in changes could be demonstrated between groups [-9.0 ms (-36; 18), P = 0.50]. Global longitudinal strain (GLS) improved in both groups [BiV group from -9.1% (±2.7) to -10.7% (±2.6), P = 0.02, and His group from -8.6% (±2.1) to -11.1% (±2.0), P < 0.001], but no significant differences in changes could be demonstrated from baseline to follow-up [-0.9% (-2.4; -0.6), P = 0.25] between groups. There were no regional differences between groups.

CONCLUSION

In heart failure, patients with LBBB, BiV-CRT, and His-CRT have comparable effects with regard to improvements in mechanical dyssynchrony and longitudinal contractile function.

Diagnostic, prognostic and clinical value of left ventricular radial strain to identify paradoxical septal motion in ventilated patients with the acute respiratory distress syndrome: an observational prospective multicenter study

BACKGROUND

Acute cor pulmonale (ACP) is prognostic in patients with acute respiratory distress syndrome (ARDS). Identification of paradoxical septal motion (PSM) using two-dimensional echocardiography is highly subjective. We sought to describe feature-engineered metrics derived from LV radial strain changes related to PSM in ARDS patients with ACP of various severity and to illustrate potential diagnostic and prognostic yield.

METHODS

This prospective bicentric study included patients under protective ventilation for ARDS related to COVID-19 who were assessed using transesophageal echocardiography (TEE). Transgastric short-axis view at mid-papillary level was used to visually grade septal motion, using two-dimensional imaging, solely and combined with LV radial strain: normal (grade 0), transient end-systolic septal flattening (grade 1), prolonged end-systolic septal flattening or reversed septal curvature (grade 2). Inter-observer variability was calculated. Feature engineering was performed to calculate the time-to-peak and area under the strain curve in 6 LV segments. In the subset of patients with serial TEE examinations, a multivariate Cox model analysis accounting for new-onset of PSM as a time-dependent variable was used to identify parameters associated with ICU mortality.

RESULTS

Overall, 310 TEE examinations performed in 182 patients were analyzed (age: 67 [60-72] years; men: 66%; SAPSII: 35 [29-40]). Two-dimensional assessment identified a grade 1 and grade 2 PSM in 100 (32%) and 48 (15%) examinations, respectively. Inter-rater reliability was weak using two-dimensional imaging alone (kappa = 0.49; 95% CI 0.40-0.58; p < 0.001) and increased with associated LV radial strain (kappa = 0.84, 95% CI 0.79-0.90, p < 0.001). The time-to-peak of mid-septal and mid-lateral segments occurred significantly later in systole and increased with the grade of PSM. Similarly, the area under the strain curve of these segments increased significantly with the grade of PSM, compared with mid-anterior or mid-inferior segments. Severe acute cor pulmonale with a grade 2 PSM was significantly associated with mortality. Requalification in an upper PSM grade using LV radial strain allowed to better identify patients at risk of death (HR: 6.27 [95% CI 2.28-17.2] vs. 2.80 [95% CI 1.11-7.09]).

CONCLUSIONS

In objectively depicting PSM and quantitatively assessing its severity, TEE LV radial strain appears as a valuable adjunct to conventional two-dimensional imaging.

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.

Early left bundle branch pacing in heart failure with mildly reduced ejection fraction and left bundle branch block

BACKGROUND

Left bundle branch pacing (LBBP) achieves resynchrony and improves cardiac function in heart failure (HF) patients with reduced ejection fraction (EF) by correcting left bundle branch block (LBBB). Few data on the efficacy of early LBBP in HF with mildly reduced EF (HFmrEF) and LBBB have been reported.

OBJECTIVE

The purpose of this study was to explore the efficacy of early LBBP in patients with HFmrEF and LBBB.

METHODS

Consecutive patients with HFmrEF (left ventricular EF [LVEF] 35%-50%) and LBBB were prospectively enrolled to receive LBBP (Early-LBBP group) plus guideline-directed medical therapy (GDMT) or GDMT alone (GDMT group). Study outcomes included changes in LVEF, LV end-diastolic diameter (LVEDD), New York Heart Association (NYHA) functional classification, and N-terminal pro-brain natriuretic peptide (NT-proBNP), and clinical events (HF rehospitalization or syncope). Subgroup analysis compared efficacy of LBBP between patients with LBBB only without comorbidities or late gadolinium enhancement (LGE) (LBBB-Only group) and patients with either comorbidities or LGE (LBBB-Combined group).

RESULTS

Fifty-four patients were enrolled and analyzed (37 Early-LBBP group; 15 GDMT group). LBBP achieved greater improvement in LVEF (+14.75% ± 7.37% vs -2.42% ± 2.84%; P <.001), reduction of LVEDD (-7.51 ± 5.40 mm vs -0.87 ± 4.36 mm; P <.001) and NYHA classification (-0.84 ± 0.76 vs -0.13 ± 0.74; P = .004), and similar reduction of NT-proBNP (-408.83 ± 920.29 pg/mL vs -229.05 ± 1579.17 pg/mL; P = .610) at 6 months. Early LBBP showed significantly reduced clinical events (0.0% vs 40.0%; P <.001) after 20.68 ± 13.55 months of follow-up. Subgroup analysis showed patients in the LBBB-Only group benefited more from LBBP with regard to LVEF improvement and LVEDD reduction than the LBBB-Combined group.

CONCLUSION

Early LBBP with GDMT demonstrated greater improvement of cardiac function and reduced clinical events than GDMT alone in patients with HFmrEF and LBBB.

Cardiac MRI-derived Myocardial Fibrosis and Ventricular Dyssynchrony Predict Response to Cardiac Resynchronization Therapy in Patients with Nonischemic Dilated Cardiomyopathy

Purpose

To determine the association of myocardial fibrosis and left ventricular (LV) dyssynchrony measured using cardiac MRI with late gadolinium enhancement (LGE) and feature tracking (FT), respectively, with response to cardiac resynchronization therapy (CRT) for nonischemic dilated cardiomyopathy (DCM).

Materials and Methods

This retrospective study included 98 patients (mean age, 59 years ± 10 [SD]; 54 men) who had nonischemic DCM, as assessed with LGE cardiac MRI before CRT. Cardiac MRI FT-derived dyssynchrony was defined as the SD of the time-to-peak strain (TTP-SD) of the LV segments in three directions (longitudinal, radial, and circumferential). CRT response was defined as a 15% increase in LV ejection fraction (LVEF) at echocardiography at 6-month follow-up, and then, long-term cardiovascular events were assessed. The likelihood ratio test was used to evaluate the incremental prognostic value of LGE and dyssynchrony parameters.

Results

Seventy-one (72%) patients showed a favorable LVEF response following CRT. LGE presence (odds ratio: 0.14 [95% CI: 0.04, 0.47], P = .002; and hazard ratio: 3.52 [95% CI: 1.37, 9.07], P = .01) and lower circumferential TTP-SD (odds ratio: 1.04 [95% CI: 1.02, 1.07], P = .002; and hazard ratio: 0.98 [95% CI: 0.96, 1.00], P = .03) were independently associated with LVEF nonresponse and long-term outcomes. Combined LGE and circumferential TTP-SD provided the highest discrimination for LVEF nonresponse (area under the receiver operating characteristic curve [AUC]: 0.89 [95% CI: 0.81, 0.94], sensitivity: 84.5% [95% CI: 74.0%, 92.0%], specificity: 85.2% [95% CI: 66.3%, 95.8%]) and long-term outcomes (AUC: 0.84 [95% CI: 0.75, 0.91], sensitivity: 76.9% [95% CI: 56.4%, 91.0%], specificity: 87.0% [95% CI: 76.7%, 93.9%]).

Conclusion

Myocardial fibrosis and lower circumferential dyssynchrony assessed with pretherapy cardiac MRI were independently associated with unfavorable LVEF response and long-term events following CRT in patients with nonischemic DCM and may provide incremental value in predicting prognosis.Keywords: MR Imaging, Cardiac, Outcomes Analysis Supplemental material is available for this article. © RSNA, 2023.

Contractile asymmetry and survival in patients with left bundle branch abnormality treated with cardiac resynchronization therapy

Aims

Currently, electrical rather than mechanical parameters of delayed left ventricular (LV) activation are used for patient selection for cardiac resynchronization therapy (CRT). However, despite adhering to current guideline-based criteria, about one-third of heart failure (HF) patients fail to derive benefit from CRT. This study sought to investigate the prognostic survival significance of a recently introduced index of contractile asymmetry (ICA) based on the deformation of entire opposing LV walls in the context of selecting patients with HF and left bundle branch abnormality (LBBB) for CRT.

Methods and results

We analysed 367 patients with HF and LBBB undergoing CRT (31.6% females, 69 ± 9 years, ischaemic aetiology in 50.7%, LV ejection fraction 27 ± 6%). ICA was calculated using LV strain rate values from curved anatomical M-mode plots of apical 2D echocardiography images. The predictive value of ICA was assessed using Kaplan-Meier analysis and Cox proportional hazards models. During a median follow-up time of 5.54 years, death or cardiac transplantation occurred in 105 (28.6%) cases. Higher baseline ICA values in all apical views, particularly in the two-chamber view (ICA-2ch), were associated with increased event-free survival, and the unadjusted hazard ratio was 0.28 (95% confidence interval 0.18-0.46). Higher ICA-2ch (>0.319 s-1) consistently predicted survival across clinical subgroups and remained significant after covariate adjustment, while the event rate sharply increased in low ICA-2ch cases. Additionally, including ICA-2ch improved the predictive value of the multivariate risk model containing the typical LBBB pattern.

Conclusion

Pre-implant ICA suggests a quantitative prognostic threshold for both long-term survival and adverse outcomes following CRT implantation.

Left Bundle Branch Block: Characterization, Definitions, and Recent Insights into Conduction System Physiology

Left bundle branch block (LBBB) is not just a simple electrocardiogram alteration. The intricacies of this general terminology go beyond simple conduction block. This review puts together current knowledge on the historical concept of LBBB, clinical significance, and recent insights into the pathophysiology of human LBBB. LBBB is an entity that affects patient diagnosis (primary conduction disease, secondary to underlying pathology or iatrogenic), treatment (cardiac resynchronization therapy or conduction system pacing for heart failure), and prognosis. Recruiting the left bundle branch with conduction system pacing depends on the complex interaction between anatomy, site of pathophysiology, and delivery tools.

Strain Imaging and Ventricular Arrhythmia

Ventricular arrhythmia is one of the main causes of sudden cardiac death. Hence, identifying patients at risk of ventricular arrhythmias and sudden cardiac death is important but can be challenging. The indication for an implantable cardioverter defibrillator as a primary preventive strategy relies on the left ventricular ejection fraction as a measure of systolic function. However, ejection fraction is flawed by technical constraints and is an indirect measure of systolic function. There has, therefore, been an incentive to identify other markers to optimize the risk prediction of malignant arrhythmias to select proper candidates who could benefit from an implantable cardioverter defibrillator. Speckle-tracking echocardiography allows for a detailed assessment of cardiac mechanics, and strain imaging has repeatedly been shown to be a sensitive technique to identify systolic dysfunction unrecognized by ejection fraction. Several strain measures, including global longitudinal strain, regional strain, and mechanical dispersion, have consequently been proposed as potential markers of ventricular arrhythmias. In this review, we will provide an overview of the potential use of different strain measures in the context of ventricular arrhythmias.

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.

Atrio-Ventricular Dyssynchrony After Cardiac Resynchronization Therapy: An Unusual Contributor to Heart Failure Symptoms

Cardiac resynchronization therapy (CRT) is the mainstay for the management of systolic heart failure with LVEF <35% and evidence of dyssynchrony despite optimal medical therapy. After CRT placement, persistent dyssynchronization is possible and can contribute to heart failure symptoms despite a well-functioning CRT device. Echo-guided imaging can be beneficial for the optimization of CRT in selected patients who have evidence of continued dyssynchrony despite a well-functioning CRT device.

Left Ventricular "Longitudinal Rotation" and Conduction Abnormalities-A New Outlook on Dyssynchrony

BACKGROUND

The complete left bundle branch block (CLBBB) results in ventricular dyssynchrony and a reduction in systolic and diastolic efficiency. We noticed a distinct clockwise rotation of the left ventricle (LV) in patients with CLBBB ("longitudinal rotation").

AIM

The aim of this study was to quantify the "longitudinal rotation" of the LV in patients with CLBBB in comparison to patients with normal conduction or complete right bundle branch block (CRBBB).

METHODS

Sixty consecutive patients with normal QRS, CRBBB, or CLBBB were included. Stored raw data DICOM 2D apical-4 chambers view images cine clips were analyzed using EchoPac plugin version 203 (GE Vingmed Ultrasound AS, Horten, Norway). In EchoPac-Q-Analysis, 2D strain application was selected. Instead of apical view algorithms, the SAX-MV (short axis-mitral valve level) algorithm was selected for analysis. A closed loop endocardial contour was drawn to initiate the analysis. The "posterior" segment (representing the mitral valve) was excluded before finalizing the analysis. Longitudinal rotation direction, peak angle, and time-to-peak rotation were recorded.

RESULTS

All patients with CLBBB (n = 21) had clockwise longitudinal rotation with mean four chamber peak rotation angle of -3.9 ± 2.4°. This rotation is significantly larger than in patients with normal QRS (-1.4 ± 3°, p = 0.005) and CRBBB (0.1 ± 2.2°, p = 0.00001). Clockwise rotation was found to be correlated to QRS duration in patients with the non-RBBB pattern. The angle of rotation was not associated with a lower ejection fraction or the presence of regional wall abnormalities.

CONCLUSIONS

Significant clockwise longitudinal rotation was found in CLBBB patients compared to normal QRS or CRBBB patients using speckle-tracking echocardiography.

State of the art: multimodality imaging in dilated cardiomyopathy

Dilated cardiomyopathy represents a common phenotype expressed in individuals with a family of overlapping myocardial diseases due to acquired and/or genetic susceptibility. Disease trajectory, response to therapy and outcomes vary widely; therefore, further refinement of the diagnosis can help guide therapy and inform prognosis. Multimodality imaging plays a key role in this process, as well as excluding alternative causes which may mimic a primary myocardial disease. The following article discusses the role of different imaging modalities as well as what the future may look like in the context of recent research innovations.

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.

Cardiac resynchronization considerations in left bundle branch block

Cardiac resynchronization therapy (CRT) via biventricular pacing (BiVP) is an established treatment for patients with left ventricular systolic heart failure and intraventricular conduction delay resulting in wide QRS. Seminal trials demonstrating mortality benefit from CRT were conducted in patients with wide left bundle branch block (LBBB) pattern on electrocardiogram (ECG) and evidence of clinical heart failure. The presence of conduction block was assumed to correlate with commonly applied criteria for LBBB. More recent data has challenged this assertion, revealing that LBBB pattern may include distinct underlying pathophysiology, including patients with complete conduction block, either at the left-sided His fibers or the proximal left bundle, intact Purkinje activation with wide LBBB-like QRS, and patients demonstrating both proximal block and distal delay. Currently, BiVP-CRT is indicated for all QRS duration ≥150 ms and may be considered for BBB patterns from 130 to 149 ms with robust clinical data to support its use. Despite this, however, there remains a significant number of non-responders to BVP. Conduction system pacing (CSP) has emerged as an alternative approach to deliver CRT and correct QRS in patients with conduction block. Newer hybrid approaches which combine CSP and traditional BiVP-CRT and may hold promise for patients with IP or mixed-level block. As various approaches to CRT continue to be studied, physiologic phenotyping of the LBBB pattern remains an important consideration.

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.

Evolving concept of dyssynchrony and its utility

The role of electromechanical dyssynchrony in heart failure gained prominence in literature with the results of trials of cardiac resynchronization therapy (CRT). CRT has shown to significantly decrease heart failure hospitalization and mortality in heart failure patients with dyssynchrony. Current guidelines recommend the use of electrical dyssynchrony based on a QRS > 150 ms and a left bundle branch block pattern on surface electrocardiogram to identify dyssynchrony in patients who will benefit from CRT implantation. However, predicting response to CRT remains a challenge with nearly one-third of patients gaining no benefit from the device. Multiple echocardiographic measures of mechanical dyssynchrony have been studied over the past two decade. However, trials where mechanical dyssynchrony used as an additional or lone criteria for CRT failed to show any benefit in the response to CRT. This shows that a deeper understanding of cardiac mechanics should be applied in the assessment of dyssynchrony. This review discusses the evolving role of imaging techniques in assessing cardiac dyssynchrony and their application in patients considered for device therapy.

Multimodality Cardiac Imaging in Cardiomyopathies: From Diagnosis to Prognosis

Cardiomyopathies are a group of structural and/or functional myocardial disorders which encompasses hypertrophic, dilated, arrhythmogenic, restrictive, and other cardiomyopathies. Multimodality cardiac imaging techniques are the cornerstone of cardiomyopathy diagnosis; transthoracic echocardiography should be the first-line imaging modality due to its availability, and diagnosis should be confirmed by cardiovascular magnetic resonance, which will provide more accurate morphologic and functional information, as well as extensive tissue characterization. Multimodality cardiac imaging techniques are also essential in assessing the prognosis of patients with cardiomyopathies; left ventricular ejection fraction and late gadolinium enhancement are two of the main variables used for risk stratification, and they are incorporated into clinical practice guidelines. Finally, periodic testing with cardiac imaging techniques should also be performed due to the evolving and progressive natural history of most cardiomyopathies.

Left Bundle Branch Block: Characterization, Definitions, and Recent Insights into Conduction System Physiology

Left bundle branch block (LBBB) is not just a simple electrocardiogram alteration. The intricacies of this general terminology go beyond simple conduction block. This review puts together current knowledge on the historical concept of LBBB, clinical significance, and recent insights into the pathophysiology of human LBBB. LBBB is an entity that affects patient diagnosis (primary conduction disease, secondary to underlying pathology or iatrogenic), treatment (cardiac resynchronization therapy or conduction system pacing for heart failure), and prognosis. Recruiting the left bundle branch with conduction system pacing depends on the complex interaction between anatomy, site of pathophysiology, and delivery tools.

Mechanical Synchrony and Myocardial Work in Heart Failure Patients With Left Bundle Branch Area Pacing and Comparison With Biventricular Pacing

Background: Little is known about the efficacy of permanent left bundle branch area pacing (LBBAP) in delivering cardiac resynchronization therapy (CRT). This study aimed to evaluate the effect of LBBAP on mechanical synchronization and myocardial work (MW) in heart failure (HF) patients and to compare LBBAP with biventricular pacing (BVP).

Methods: This is a multicenter, prospective cohort study. From February 2018 to January 2021, 62 consecutive HF patients with reduced ejection fraction (LVEF ≤ 35%) and complete left bundle branch block (CLBBB) who underwent LBBAP or BVP were enrolled in this study. Echocardiograms and electrocardiograms and were conducted before and 3–6 months after implantation. Intra- and interventricular synchronization were assessed using two-dimensional speckle tracking imaging (2D-STI). The left ventricular pressure-strain loop was obtained by combining left ventricular strain with non-invasive blood pressure to evaluate mechanical efficiency.

Results: The echocardiographic response rates were 68.6 and 88.9% in the BVP and LBBAP groups, respectively. Left bundle branch area pacing resulted in significant QRS narrowing (from 177.1 ± 16.7 to 113.0 ± 18.4 ms, P < 0.001) and improvement in LVEF (from 29.9 ± 4.8 to 47.1 ± 8.3%, P < 0.001). The global wasted work (GWW) (410.3 ± 166.6 vs. 283.0 ± 129.6 mmHg%, P = 0.001) and global work efficiency (GWE) (64.6 ± 7.8 vs. 80.5 ± 5.7%, P < 0.001) were significantly improved along with shorter peak strain dispersion (PSD) (143.4 ± 45.2 vs. 92.6 ± 35.1 ms, P < 0.001) and interventricular mechanical delay (IVMD) (56.4 ± 28.5 vs. 28.9 ± 19.0 ms, P < 0.001), indicating its efficiency in improving mechanical synchronization. In comparison with BVP, LBBAP delivered greater improvement of QRS narrowing (−64.1 ± 18.9 vs. −32.5 ± 22.3 ms, P < 0.001) and better mechanical synchronization and efficiency.

Conclusions: Left bundle branch area pacing was effective in improving cardiac function, mechanical synchronization, and mechanical efficiency and may be a promising alternative cardiac resynchronization therapy.

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.

Segment Length in Cine Strain Analysis Predicts Cardiac Resynchronization Therapy Outcome Beyond Current Guidelines

BACKGROUND

Patients with a class I recommendation for cardiac resynchronization therapy (CRT) are likely to benefit, but the effect of CRT in class II patients is more heterogeneous and additional selection parameters are needed in this group. The recently validated segment length in cine strain analysis of the septum (SLICE-ESS_sep) measurement on cardiac magnetic resonance cine imaging predicts left ventricular functional recovery after CRT but its prognostic value is unknown. This study sought to evaluate the prognostic value of SLICE-ESS_sep for clinical outcome after CRT.

METHODS

Two hundred eighteen patients with a left bundle branch block or intraventricular conduction delay and a class I or class II indication for CRT who underwent preimplantation cardiovascular magnetic resonance examination were enrolled. SLICE-ESS_sep was manually measured on standard cardiovascular magnetic resonance cine imaging. The primary combined end point was all-cause mortality, left ventricular assist device, or heart transplantation. Secondary end points were (1) appropriate implantable cardioverter defibrillator therapy and (2) heart failure hospitalization.

RESULTS

Two-thirds (65%) of patients had a positive SLICE-ESS_sep ≥0.9% (ie, systolic septal stretching). During a median follow-up of 3.8 years, 66 (30%) patients reached the primary end point. Patients with positive SLICE-ESS_sep were at lower risk to reach the primary end point (hazard ratio 0.36; P<0.001) and heart failure hospitalization (hazard ratio 0.41; P=0.019), but not for implantable cardioverter defibrillator therapy (hazard ratio, 0.66; P=0.272). Clinical outcome of class II patients with a positive ESS_sep was similar to those of class I patients (hazard ratio, 1.38 [95% CI, 0.66-2.88]; P=0.396).

CONCLUSIONS

Strain assessment of the septum (SLICE-ESS_sep) provides a prognostic measure for clinical outcome after CRT. Detection of a positive SLICE-ESS_sep in patients with a class II indication predicts improved CRT outcome similar to those with a class I indication whereas SLICE-ESS_sep negative patients have poor prognosis after CRT implantation.

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.

Echocardiographic view and feature selection for the estimation of the response to CRT

Cardiac resynchronization therapy (CRT) is an implant-based therapy applied to patients with a specific heart failure (HF) profile. The identification of patients that may benefit from CRT is a challenging task and the application of current guidelines still induce a non-responder rate of about 30%. Several studies have shown that the assessment of left ventricular (LV) mechanics by speckle tracking echocardiography can provide useful information for CRT patient selection. A comprehensive evaluation of LV mechanics is normally performed using three different echocardioraphic views: 4, 3 or 2-chamber views. The aim of this study is to estimate the relative importance of strain-based features extracted from these three views, for the estimation of CRT response. Several features were extracted from the longitudinal strain curves of 130 patients and different methods of feature selection (out-of-bag random forest, wrapping and filtering) have been applied. Results show that more than 50% of the 20 most important features are calculated from the 4-chamber view. Although features from the 2- and 3-chamber views are less represented in the most important features, some of the former have been identified to provide complementary information. A thorough analysis and interpretation of the most informative features is also provided, as a first step towards the construction of a machine-learning chain for an improved selection of CRT candidates.

Assessing left ventricular systolic function: from ejection fraction to strain analysis

The measurement of left ventricular ejection fraction (LVEF) is a ubiquitous component of imaging studies used to evaluate patients with cardiac conditions and acts as an arbiter for many management decisions. This follows early trials investigating heart failure therapies which used a binary LVEF cut-off to select patients with the worst prognosis, who may gain the most benefit. Forty years on, the cardiac disease landscape has changed. Left ventricular ejection fraction is now a poor indicator of prognosis for many heart failure patients; specifically, for the half of patients with heart failure and truly preserved ejection fraction (HF-PEF). It is also recognized that LVEF may remain normal amongst patients with valvular heart disease who have significant myocardial dysfunction. This emphasizes the importance of the interaction between LVEF and left ventricular geometry. Guidelines based on LVEF may therefore miss a proportion of patients who would benefit from early intervention to prevent further myocardial decompensation and future adverse outcomes. The assessment of myocardial strain, or intrinsic deformation, holds promise to improve these issues. The measurement of global longitudinal strain (GLS) has consistently been shown to improve the risk stratification of patients with heart failure and identify patients with valvular heart disease who have myocardial decompensation despite preserved LVEF and an increased risk of adverse outcomes. To complete the integration of GLS into routine clinical practice, further studies are required to confirm that such approaches improve therapy selection and accordingly, the outcome for patients.

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.

The value of non-invasive myocardial work indices derived from left ventricular pressure-strain loops in predicting the response to cardiac resynchronization therapy

Background

Non-invasive left ventricular (LV) pressure-strain loops (PSLs), which are generated by combining LV longitudinal strain with brachial artery blood pressure, provide a novel method of quantifying global and segmental myocardial work (MW) indices with potential advantages over conventional echocardiographic strain data, which suffers from being load-dependent. This method has been recently introduced in echocardiographic software, enhancing the efficiency of MW calculations. This study aimed to evaluate the role of non-invasive MW indices derived from LV PSLs in predicting cardiac resynchronization therapy (CRT) response.

Methods

A total of 106 heart failure (HF) patients scheduled for CRT were included in the MW analysis. Global and segmental (septal and lateral at the mid-ventricular level) MW indices were assessed before CRT and at a 6-month follow-up. Response to CRT was defined as ≥15% reduction in LV end-systolic volume and ≥1 NYHA functional class improvement at 6-month follow-up compared to baseline.

Results

CRT response was observed in 78 (74%) patients. At baseline, the global work index (GWI) and global constructive work (GCW) were significantly higher in CRT responders than in non-responders (both P<0.05). Furthermore, responders exhibited significantly higher mid lateral MW and mid lateral constructive work (CW) (both P<0.001), but significantly lower mid septal MWI and mid septal myocardial work efficiency (MWE) than non-responders (all P<0.01). Baseline mid septal MWE (OR 0.975, 95% CI: 0.959-0.990, P=0.002) and mid lateral MWI (OR 1.003, 95% CI: 1.002-1.004, P<0.001) were identified as independent predictors of CRT response in multivariate regression analysis. Mid septal MWE ≤42% combined with mid lateral MWI ≥740 mmHg% predicted CRT response, with an optimal sensitivity of 79% and specificity of 82% [area under the receiver operating characteristic curve (AUC) =0.830, P<0.001].

Conclusions

Assessment of MW indices before CRT could identify the marked imbalance in LV MW distribution and can be widely used as a reliable complementary tool for guiding patient selection for CRT in clinical practice.

Left bundle branch block without a typical contraction pattern is associated with increased risk of ventricular arrhythmias in cardiac resynchronization therapy patients

Cardiac resynchronization therapy (CRT) reduces the risk of ventricular arrhythmias (VA) in heart failure (HF) patients with left bundle branch block (LBBB) while the effect is less clear among non-LBBB patients. This study aimed to investigate if absence of LBBB features whether by echocardiography or strict ECG criteria would identify patients at risk of developing VA in a cohort with LBBB according to conventional ECG criteria. Two hundred six CRT candidates were prospectively included from 2 centers. Prior to CRT presence of a typical LBBB contraction pattern was identified using longitudinal strain in the apical 4-chamber view. All preimplantation ECGs were categorized as LBBB or non-LBBB according to Strauss´ strict criteria. Primary end-point was defined as any appropriate antitachycardia pacing (ATP) or shock therapy within 2 years after CRT implantation. A total of 129 (63%) patients had a typical LBBB contraction pattern, while 134 (66%) met the strict ECG criteria. Over 2 years, 45 patients (22%) experienced VA. Absence of a typical LBBB contraction pattern was independently associated with an increased risk of VA (hazard ratio ([HR] 1.89; 95% CI 1.04 to 3.44; p: 0.036). Strict LBBB was not independently associated with the occurrence of VA. Fulfilling neither strict ECG nor echocardiographic criteria for LBBB was associated with a 3.3-fold increase in risk of VA ([HR] 3.34; 95% CI 1.75 to 6.94; (p < 0.001). The risk of VA was almost 2-fold higher if a typical LBBB contraction pattern was absent prior to CRT.

Clinical Utility of Echocardiographic Strain and Strain Rate Measurements

PURPOSE OF REVIEW

Assessment of left ventricular function is pivotal in many decisions, but ejection fraction has fundamental limitations for assessment of mild dysfunction, and especially for repeated assessments. Myocardial deformation imaging using speckle-tracking is widely available on modern echocardiography systems, and is now feasible as a clinical, rather than purely a research tool. Strain can be measured in all cardiac chambers, most commonly as a systolic parameter, although it can be measured in diastole. Generally, speckle tracking is more effective at measuring strain than strain-rate, which requires a higher temporal resolution. The purpose of this review is to help clinicians understand the main situations where strain provides incremental value to standard echocardiographic measurements.

RECENT FINDINGS

The normal range of LV global longitudinal strain (GLS) has now been defined as -18% and lower (ie more negative), abnormal as -16% or higher (ie less negative), with -16 to -18% being borderline. The variation between different vendors is now small for global parameters, but regional strain measurement remains unreliable - and therefore its use for stress echocardiography remains problematic. The most valuable indications for measuring strain are subclinical LV dysfunction (eg., GLS in HFpEF, stage B heart failure, aortic stenosis, mitral regurgitation), RV dysfunction (RV strain in pulmonary hypertension), atrial fibrillation (LA strain) and sequential follow-up (cardiotoxicity). Strain measurements have clinical utility in a number of settings and should be considered as part of the standard echocardiogram.

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.