Global myocardial work index predicts response to biventricular pacing in patients with non-left bundle branch block

AIMS

Cardiac resynchronization therapy (CRT) improves the prognosis of patients with heart failure (HF) and wide QRS complex. However, patients with non-left bundle branch block (LBBB) show a poor response to CRT. This study evaluated myocardial work estimated by pressure-strain loops on echocardiography for predicting response to CRT in patients with non-LBBB.

METHODS AND RESULTS

Of 267 patients who underwent CRT implantation, 54 patients with non-LBBB (mean age, 62 ± 12 years, 72% males, and 24% with ischemic cardiomyopathy) were retrospectively included. Two-dimensional speckle-tracking echocardiography was performed before and at 6-month follow-up in all patients. Myocardial work was estimated by pressure-strain loop analysis using speckle-tracking echocardiography and non-invasive blood pressure measurement. CRT response was defined as a ≥15% decrease in left ventricular end-systolic volume on echocardiography at the 6-month follow-up. The mean left ventricular ejection fraction (LVEF) before implantation was 27% ± 8% in total. Six months after implantation, 18 patients (33%) responded to CRT. The absolute LVEF improvement for responders and non-responders were 5.5% ± 6.9% and 1.3% ± 7.5%, respectively (P = 0.021). Baseline global work index (GWI), which is the average myocardial work based on the pressure-strain loop, was significantly higher in the responder group than in the non-responder group (590 ± 271 vs. 409 ± 216 mmHg%; P = 0.010). Multivariable analysis showed GWI to be an independent predictor of CRT response (odds ratio, 1.109; 95% confidence interval [CI], 1.013-1.213; P = 0.024). Receiver operating characteristic curve analysis determined the cut-off value of GWI for response as 456 mmHg% (AUC 0.700, 95% CI 0.553-0.840; P = 0.019). During the median 37-month follow-up, all-cause death occurred in 21 patients (39%). On multivariable analysis, GWI ≤ 456 mmHg% was independently associated with an increased risk of all-cause mortality (hazard ratio, 2.882; 95% CI, 1.157-7.176; P = 0.023).

CONCLUSIONS

High GWI assessed by speckle-tracking echocardiography and a non-invasively estimated LV pressure curve was independently associated with a favourable response to CRT and improved outcomes in patients with non-LBBB. The use of this non-invasive approach for quantifying myocardial variability and residual contractility can be beneficial for assessing CRT candidates and allow for more accurate patient stratification. Further, large multicentre studies are required to validate these findings.

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.

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.

A Comparative Analysis of Apical Rocking and Septal Flash: Two Views of the Same Systole?

Heart failure (HF) is a complex medical condition characterized by both electrical and mechanical dyssynchrony. Both dyssynchrony mechanisms are intricately linked together, but the current guidelines for cardiac resynchronization therapy (CRT) rely only on the electrical dyssynchrony criteria, such as the QRS complex duration. This possible inconsistency may result in undertreating eligible individuals who could benefit from CRT due to their mechanical dyssynchrony, even if they fail to fulfill the electrical criteria. The main objective of this literature review is to provide a comprehensive analysis of the practical value of echocardiography for the assessment of left ventricular (LV) dyssynchrony using parameters such as septal flash and apical rocking, which have proven their relevance in patient selection for CRT. The secondary objectives aim to offer an overview of the relationship between septal flash and apical rocking, to emphasize the primary drawbacks and benefits of using echocardiography for evaluation of septal flash and apical rocking, and to offer insights into potential clinical applications and future research directions in this area. Conclusion: there is an opportunity to render resynchronization therapy more effective for every individual; septal flash and apical rocking could be a very useful and straightforward echocardiography resource.

Concepts of Cardiac Dyssynchrony and Dynamic Approach

Cardiac conduction involves electrical activity from one myocyte to another, creating coordinated contractions in each. Disruptions in the conducting system, such as left bundle branch block (LBBB), can result in premature activation of specific regions of the heart, leading to heart failure and increased morbidity and mortality. Structural alterations in T-tubules and the sarcoplasmic reticulum can lead to dyssynchrony, a condition that can be treated by cardiac resynchronization therapy (CRT), which stands as a cornerstone in this pathology. The heterogeneity in patient responses underscored the necessity of improving the diagnostic approach. Vectocardiography, ultra-high-frequency ECG, 3D echocardiography, and electrocardiographic imaging seem to offer advanced precision in identifying optimal candidates for CRT in addition to the classic diagnostic methods. The advent of His bundle pacing and left bundle branch pacing further refined the approach in the treatment of dyssynchrony, offering more physiological pacing modalities that promise enhanced outcomes by maintaining or restoring the natural sequence of ventricular activation. HOT-CRT emerges as a pivotal innovation combining the benefits of CRT with the precision of His bundle or left bundle branch area pacing to optimize cardiac function in a subset of patients where traditional CRT might fall short.

Potential Underestimation of Left Ventricular Mechanical Dyssynchrony in Dyssynchrony and Outcomes Assessment

Objective

Left ventricular (LV) mechanical dyssynchrony (LVMD) is fundamental to the progression of heart failure and ventricular remodeling. The status of LVMD in different patterns of bundle branch blocks (BBB) is unclear. In this study, we analyzed the relationship between LVMD and left ventricular systolic dysfunction using real-time three-dimensional echocardiography (RT-3DE).

Methods

RT-3DE and conventional two-dimensional echocardiography were performed on 68 patients with left bundle branch block (LBBB group), 106 patients with right bundle branch block (RBBB group), and 103 patients without BBB (Normal group). The RT-3DE data sets provided time-volume analysis for global and segmental LV volumes. The LV systolic dyssynchrony index (LVSDI) was calculated using the standard deviation (SD) and maximal difference (Dif) of time to minimum segmental volume (tmsv) for LV segments adjusted by the R-R interval. LVMD was considered if the LVSDI (Tmsv-16-SD) was greater than or equal to 5%.

Results

LVSDI is negatively and significantly correlated with left ventricular ejection fraction (LVEF), but not with BBB or QRS duration. The proportion of LVMD in the LBBB, RBBB, and Normal group was 30.88%, 28.30%, and 25.24%, respectively, and there was no significant difference.

Conclusion

In dilated cardiomyopathy, LVMD is more closely related to LVEF reduction than QRS morphology and duration.

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.

Echocardiographic mechanical dyssynchrony predicts long-term mortality in patients with cardiac resynchronisation therapy

Cardiac resynchronisation therapy (CRT) is an established treatment for patients with symptomatic heart failure with reduced left ventricular ejection fraction (LVEF ≤ 35%; HFrEF) and conduction disturbances (QRS duration ≥ 130 ms). The presence of mechanical dyssynchrony (MD) on echocardiography has been hypothesised to be of predictive value in determining indication for CRT. This study investigated the impact of MD (apical rocking [AR] and septal flash [SF]) on long-term survival in CRT recipients. HFrEF patients (n = 425; mean age 63.0 ± 10.6 years, 72.3% male, 60.7% non-ischaemic aetiology) with a guideline-derived indication for CRT underwent device implantation. MD markers were determined at baseline and after a mean follow-up of 11.5 ± 8.0 months; long-term survival was also determined. AR and/or SF were present in 307 (72.2%) participants at baseline. During post-CRT follow-up, AR and/or SF disappeared in 256 (83.4%) patients. Overall mean survival was 95.9 ± 52.9 months, longer in women than in men (109.1 ± 52.4 vs. 90.9 ± 52.4 months; p < 0.001) and in younger (< 60 years) versus older patients (110.6 ± 53.7 vs. 88.6 ± 51.1 months; p < 0.001). Patients with versus without MD markers at baseline generally survived for longer (106.2 ± 52.0 vs. 68.9 ± 45.4 months; p < 0.001), and survival was best in patients with resolved versus persisting MD (111.6 ± 51.2 vs. 79.7 ± 47.6 months p < 0.001). Age and MD at baseline were strong predictors of long-term survival in HFrEF patients undergoing CRT on multivariate analysis. Novel echocardiography MD parameters in HFrEF CRT recipients predicted long-term mediated better outcome, and survival improved further when AR and/or SF disappear after CRT implantation.

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).

Tetralogy of Fallot Across the Lifespan: A Focus on the Right Ventricle

Tetralogy of Fallot is a cyanotic congenital heart disease, for which various surgical techniques allow patients to survive to adulthood. Currently, the natural history of corrected tetralogy of Fallot is underlined by progressive right ventricular (RV) failure due to pulmonic regurgitation and other residual lesions. The underlying cellular mechanisms that lead to RV failure from chronic volume overload are characterized by microvascular and mitochondrial dysfunction through various regulatory molecules. On a clinical level, these cardiac alterations are commonly manifested as exercise intolerance. The degree of exercise intolerance can be objectified and aid in prognostication through cardiopulmonary exercise testing. The timing for reintervention on residual lesions contributing to RV volume overload remains controversial; however, interval assessment of cardiac function and volumes by echocardiography and magnetic resonance imaging may be helpful. In patients who develop clinically important RV failure, clinicians should aim to maintain a euvolemic state through the use of diuretics while paying particular attention to preload and kidney function. In patients who develop signs of cardiogenic shock from right heart failure, stabilization through the use of inotropes and pressor is indicated. In special circumstances, the use of mechanical support may be appropriate. However, cardiologists should pay particular attention to residual lesions that may impact the efficacy of the selected device.

Cardiac Magnetic Resonance Identifies Responders to Cardiac Resynchronization Therapy with an Assessment of Septal Scar and Left Ventricular Dyssynchrony

Background: The response to cardiac resynchronization therapy (CRT) depends on septal viability and correction of abnormal septal motion. This study investigates if cardiac magnetic resonance (CMR) as a single modality can identify CRT responders with combined imaging of pathological septal motion (septal flash) and septal scar. Methods: In a prospective, multicenter, observational study of 136 CRT recipients, septal scar was assessed using late gadolinium enhancement (LGE) (n = 127) and septal flash visually from cine CMR sequences. The primary endpoint was CRT response, defined as ≥15% reduction in LV end-systolic volume with echocardiography after 6 months. The secondary endpoint was heart transplantation or death of any cause assessed after 39 ± 13 months. Results: Septal scar and septal flash were independent predictors of CRT response in multivariable analysis (both p < 0.001), while QRS duration and morphology were not. The combined approach of septal scar and septal flash predicted CRT response with an area under the curve of 0.86 (95% confidence interval (CI): 0.78-0.94) and was a strong predictor of long-term survival without heart transplantation (hazard ratio 0.27, 95% CI: 0.10-0.79). The accuracy of the approach was similar in the subgroup with intermediate (130-150 ms) QRS duration. The combined approach was superior to septal scar and septal flash alone (p < 0.01). Conclusions: The combined assessment of septal scar and septal flash using CMR as a single-image modality identifies CRT responders with high accuracy and predicts long-term survival.

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.

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.

Cardiovascular imaging in conduction system pacing: What does the clinician need?

Permanent pacemakers are used for symptomatic bradycardia and biventricular pacing (BVP)-cardiac resynchronization therapy (BVP-CRT) is established for heart failure (HF) patients traditionally. According to guidelines, patients' selection for CRT is based on QRS duration (QRSd) and morphology by surface electrocardiogram (ECG). Cardiovascular imaging techniques evaluate cardiac structure and function as well as identify pathophysiological substrate changes including the presence of scar. Cardiovascular imaging helps by improving the selection of candidates, guiding left ventricular (LV) lead placement, and optimization devices during the follow-up. Conduction system pacing (CSP) includes His bundle pacing (HBP) and left bundle branch pacing (LBBP) which is screwed into the interventricular septum. CSP maintains and restores ventricular synchrony in patients with native narrow QRSd and left bundle branch block (LBBB), respectively. LBBP is more feasible than HBP due to a wider target area. This review highlights the role of multimodality cardiovascular imaging including fluoroscopy, echocardiography, cardiac magnetic resonance (CMR), myocardial scintigraphy, and computed tomography (CT) in the pre-procedure assessment for CSP, better selection for CSP candidates, the guidance of CSP lead implantation, and the optimization of devices programming after the procedure. We also compare the different characteristics of multimodality imaging and discuss their potential roles in future CSP implantation.

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.

Right Ventricular Electromechanical Dyssynchrony and Its Relation to Right Ventricular Remodeling, Dysfunction, and Exercise Capacity in Ebstein Anomaly

BACKGROUND

Abnormal atrioventricular and intraventricular electrical conduction and dysfunction of the functional right ventricle (fRV) are common in Ebstein anomaly (EA). However, fRV mechanical dyssynchrony and its relation to fRV function are poorly characterized. We evaluated fRV mechanical dyssynchrony in EA patients in relation to fRV remodeling, dysfunction, and exercise intolerance.

METHODS

We retrospectively analyzed data from nonoperated EA patients and age-matched controls who underwent echocardiography, cardiovascular magnetic resonance imaging, and cardiopulmonary exercise testing to quantify right ventricular (RV) remodeling, dysfunction, and exercise capacity. The relation of these to fRV dyssynchrony was retrospectively investigated. Right ventricular mechanical dyssynchrony was defined by early fRV septal activation (right-sided septal flash), RV lateral wall prestretch/late contraction, postsystolic shortening, and intra-RV delay using two-dimensional strain echocardiography. The SD of time to peak shortening among the fRV segments was calculated as a parameter of mechanical dispersion.

RESULTS

Thirty-five EA patients (10 of whom were <18 years of age) and 35 age-matched controls were studied. Ebstein anomaly patients had worse RV function and increased intra-RV dyssynchrony versus controls. Nineteen of 35 (54%) EA patients had early septal activation with simultaneous stretch and consequent late activation and postsystolic shortening of RV lateral segments. Intra-fRV mechanical delay correlated with fRV end-diastolic volume index (r = 0.43, P < .05) and fRV end-systolic volume index (r = 0.63, P < .001). The fRV ejection fraction was lower in EA with versus without right-sided septal flash (44.9 ± 11.0 vs 54.2 ± 8.2, P = .012). The fRV mechanical dispersion correlated with the percentage of predicted peak VO₂ (r = -0.35, P < .05).

CONCLUSIONS

In EA, fRV mechanical dyssynchrony is associated with fRV remodeling, dysfunction, and impaired exercise capacity. Mechanical dyssynchrony as a therapeutic target in selected EA patients warrants further study.

Dyssynchronous Heart Failure: A Clinical Review

PURPOSE OF THE REVIEW

Dyssynchrony occurs when portions of the cardiac chambers contract in an uncoordinated fashion. Ventricular dyssynchrony primarily impacts the left ventricle and may result in heart failure. This entity is recognized as a major contributor to the development and progression of heart failure. A hallmark of dyssynchronous heart failure (HF_d) is left ventricular recovery after dyssynchrony is corrected. This review discusses the current understanding of pathophysiology of HF_d and provides clinical examples and current techniques for treatment.

RECENT FINDINGS

Data show that HF_d responds poorly to medical therapy. Cardiac resynchronization therapy (CRT) in the form of conventional biventricular pacing (BVP) is of proven benefit in HF_d, but is limited by a significant non-responder rate. Recently, conduction system pacing (His bundle or left bundle branch area pacing) has also shown promise in correcting HF_d. HF_d should be recognized as a distinct etiology of heart failure; HF_d responds best to CRT.

A multimodal deep learning model for cardiac resynchronisation therapy response prediction

We present a novel multimodal deep learning framework for cardiac resynchronisation therapy (CRT) response prediction from 2D echocardiography and cardiac magnetic resonance (CMR) data. The proposed method first uses the 'nnU-Net' segmentation model to extract segmentations of the heart over the full cardiac cycle from the two modalities. Next, a multimodal deep learning classifier is used for CRT response prediction, which combines the latent spaces of the segmentation models of the two modalities. At test time, this framework can be used with 2D echocardiography data only, whilst taking advantage of the implicit relationship between CMR and echocardiography features learnt from the model. We evaluate our pipeline on a cohort of 50 CRT patients for whom paired echocardiography/CMR data were available, and results show that the proposed multimodal classifier results in a statistically significant improvement in accuracy compared to the baseline approach that uses only 2D echocardiography data. The combination of multimodal data enables CRT response to be predicted with 77.38% accuracy (83.33% sensitivity and 71.43% specificity), which is comparable with the current state-of-the-art in machine learning-based CRT response prediction. Our work represents the first multimodal deep learning approach for CRT response prediction.

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.

Septal Flash Correction with His-Purkinje Pacing Predicts Echocardiographic Response in Resynchronization Therapy

Background

His‐Purkinje conduction system pacing (HPCSP) has been proposed as an alternative to Cardiac Resynchronization Therapy (CRT); however, predictors of echocardiographic response have not been described in this population. Septal flash (SF), a fast contraction and relaxation of the septum, is a marker of intraventricular dyssynchrony.

Methods

The study aimed to analyze whether HPCSP corrects SF in patients with CRT indication, and if correction of SF predicts echocardiographic response. This retrospective analysis of prospectively collected data included 30 patients. Left ventricular ejection fraction (LVEF) was measured with echocardiography at baseline and at 6‐month follow‐up. Echocardiographic response was defined as increase in five points in LVEF.

Results

HPCSP shortened QRS duration by 48 ± 21 ms and SF was significantly decreased (baseline 3.6 ± 2.2 mm vs. HPCSP 1.5 ± 1.5 mm p < .0001). At 6‐month follow‐up, mean LVEF improvement was 8.6% ± 8.7% and 64% of patients were responders. There was a significant correlation between SF correction and increased LVEF (r = .61, p = .004). A correction of ≥1.5 mm (baseline SF – paced SF) had a sensitivity of 81% and 80% specificity to predict echocardiographic response (area under the curve 0.856, p = .019).

Conclusion

HPCSP improves intraventricular dyssynchrony and results in 64% echocardiographic responders at 6‐month follow‐up. Dyssynchrony improvement with SF correction may predict echocardiographic response at 6‐month follow‐up.

Quality Assurance of Segmental Strain Values Provided by Commercial 2-D Speckle Tracking Echocardiography Using in Silico Models: A Report from the EACVI-ASE Strain Standardization Task Force

The aim of this study was to determine the accuracy and reproducibility of vendor-specific regional strain values by echocardiography using in silico data. Synthetic 2-D ultrasound gray-scale images of the left ventricle (LV) were generated with knowledge of the longitudinal segmental strain values from the underlying electromechanical LV model. Four of five models mimicked transmural infarctions with systolic segmental stretching in different vascular areas. Cine loops in the three apical views were synthetically generated at four noise levels. All in silico images were repeatedly analyzed by a single investigator and some by another investigator. The absolute errors varied significantly between vendors from 3.3 ± 3.1% to 11.2 ± 5.9%. The area under the curve for the identification of segmental stretching ranged from 0.80 (confidence interval: 0.77-0.83) to 0.96 (0.95-0.98). The levels of agreement for intra-investigator variability varied between -3.0% to 2.9% and -5.2% to 4.8%, and for inter-investigator variability, between -3.6% to 3.5% and -14.5% to 8.5%. Segmental strain analysis allows the identification of areas with segmental stretching with good accuracy. However, single segmental peak-strain values are not accurate and should be interpreted with caution. Nevertheless, our results indicate the usefulness of semiquantitative strain assessment for the detection of regional dysfunction.

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.

Relationship of Mechanical Dyssynchrony and LV Remodeling With Improvement of Mitral Regurgitation After CRT

OBJECTIVES

The aim of this study was to explore the association between mechanical dyssynchrony of the left ventricle before cardiac resynchronization therapy (CRT) and improvement of mitral regurgitation (MR) after CRT.

BACKGROUND

MR is very frequent among patients with dilated cardiomyopathy and conduction delay.

METHODS

Echocardiograms (pre-CRT and 12 ± 3.8 months thereafter) of 314 patients with dilated cardiomyopathy and any degree of MR, who underwent CRT device implantation according to guidelines, were analyzed. Left ventricular (LV) mechanical dyssynchrony was assessed by apical rocking (ApRock) and septal flash (SF), while MR severity was graded from I to IV on the basis of vena contracta width, regurgitation jet size, and proximal isovelocity surface area.

RESULTS

At baseline, 30% of patients presented with severe MR (grade III or IV). In 62% of patients, MR decreased after CRT, and these patients more frequently had left bundle branch block, had more severe MR, had more dilated left ventricles, had lower ejection fractions, and more often had ApRock and SF. Reverse remodeling was more frequent among patients with MR reduction (ΔLV end-systolic volume -35.5% ± 27.2% vs -4.1% ± 33.2%; P < 0.001). In a multivariable logistic stepwise regression, only ApRock (odds ratio [OR]: 3.8; 95% CI: 1.7-8.5; P = 0.001), SF (OR: 3.6; 95% CI: 1.6-7.9; P = 0.002), and baseline MR (OR: 1.4; 95% CI: 1.0-1.9; P = 0.046) remained significantly associated with MR reduction.

CONCLUSIONS

ApRock, SF, and severity of MR at baseline are strongly associated with MR reduction after CRT, while LV reverse remodeling is its underlying mechanism. Therefore, in patients with heart failure with LV dyssynchrony on optimal medical treatment, CRT should be the primary treatment attempt for relevant MR.

Septal Flash as a Predictor of Cardiac Resynchronization Therapy Response: A Systematic Review and Meta-Analysis

Cardiac resynchronization therapy (CRT) in heart failure patients has been shown to improve patient outcomes in some but not all patients. A few studies have identified that septal flash on imaging is associated with response to CRT, but there has yet to be systematic review to evaluate the consistency of the finding across the literature. A search of MEDLINE and EMBASE was conducted to identify studies, which evaluate septal flash and its association with CRT response. Studies that met the inclusion criteria were statistically pooled with random-effects meta-analysis and heterogeneity was assessed using the I2 statistic. A total of nine studies were included with 2307 participants (mean age 76 years, 67% male). Septal flash on imaging before CRT implantation was seen in 53% of patients and the proportion of CRT responders from the included studies varied from 52% to 77%. In patients who were CRT responders, septal flash was seen in 40% of patients compared to 10% in those deemed to be CRT nonresponders. Meta-analysis of eight of the nine included studies suggests that the presence of septal flash at preimplant was associated with an increased likelihood of CRT response (relative risk 2.55 95% confidence interval 2.04-3.19, P < 0.001, I2 = 51%). Septal flash was also reported to be associated with left ventricular reverse remodeling, but the association with survival and symptomatic improvement was less clear. Septal flash is a well-defined and distinctive contraction pattern that is easily recognizable on cardiac imaging. Septal flash may be associated with CRT response and should be evaluated in the patients that are considered for CRT devices.

Left atrial strain is a predictor of left ventricular systolic and diastolic reverse remodelling in CRT candidates

AIMS

The left atrium (LA) has a pivotal role in cardiac performance and LA deformation is a well-known prognostic predictor in several clinical conditions including heart failure with reduced ejection fraction. The aim of this study is to investigate the effect of cardiac resynchronization therapy (CRT) on both LA morphology and function and to assess the impact of LA reservoir strain (LARS) on left ventricular (LV) systolic and diastolic remodelling after CRT.

METHODS AND RESULTS

Two hundred and twenty-one CRT-candidates were prospectively included in the study in four tertiary centres and underwent echocardiography before CRT-implantation and at 6-month follow-up (FU). CRT-response was defined by a 15% reduction in LV end-systolic volume. LV systolic and diastolic remodelling were defined as the percent reduction in LV end-systolic and end-diastolic volume at FU. Indexed LA volume (LAVI) and LV-global longitudinal (GLS) strain were the main parameters correlated with LARS, with LV-GLS being the strongest determinant of LARS (r = -0.59, P < 0.0001). CRT induced a significant improvement in LAVI and LARS in responders (both P < 0.0001). LARS was an independent predictor of both LV systolic and diastolic remodelling at follow-up (r = -0.14, P = 0.049 and r = -0.17, P = 0.002, respectively).

CONCLUSION

CRT induces a significant improvement in LAVI and LARS in responders. In CRT candidates, the evaluation of LARS before CRT delivery is an independent predictor of LV systolic and diastolic remodelling at FU.

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.

The non-invasive assessment of myocardial work by pressure-strain analysis: clinical applications

Pressure–volume (PV) analysis is the most comprehensive way to describe cardiac function, giving insights into cardiac mechanics and energetics. However, PV analysis still remains a highly invasive and time-consuming method, preventing it from integration into clinical practice. Most of the echocardiographic parameters currently used in the clinical routine to characterize left ventricular (LV) systolic function, such as LV ejection fraction and LV global longitudinal strain, do not take the pressure developed within the LV into account and therefore fall too short in describing LV function as a hydraulic pump. Recently, LV pressure-strain analysis has been introduced as a new technique to assess myocardial work in a non-invasive fashion. This new method showed new insights in comparison to invasive measurements and was validated in different cardiac pathologies, e.g., for the detection of coronary artery disease, cardiac resynchronization therapy (CRT)-response prediction, and different forms of heart failure. Non-invasively assessed myocardial work may play a major role in guiding therapies and estimating prognosis. However, its incremental prognostic validity in comparison to common echocardiographic parameters remains unclear. This review aims to provide an overview of pressure-strain analysis, including its current application in the clinical arena, as well as potential fields of exploitation.

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

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

The mechanism and prognosis of acute and late improvement in mitral regurgitation after cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) improves functional mitral regurgitation (MR); however, the mechanism and differences in acute and late improvement in MR are unclear. We aimed to evaluate the factors associated with the acute and late MR improvements and the prognosis of MR improvement after CRT. This retrospective study included 121 patients who underwent CRT implantation with full echocardiography assessment at baseline, 1 week, and 6 months after implantation. MR severity was classified into five grades (0: none to 4: severe). Two-dimensional speckle-tracking echocardiography with radial strain was used to assess dyssynchrony, and the time difference between the lateral and inferior segments at papillary muscle levels (TD_late-inf) was calculated. The MR improved 1 week and 6 months after CRT in 40 (33%) and 45 (37%) patients, respectively. On multivariate analyses, TD_late-inf (baseline-1 week) and SPWMD were independently associated with acute MR improvement. The %reduction in left ventricular end-systolic volume (LVESV) (baseline-6 months) and TD_late-inf (baseline-1 week) were independently correlated with late MR improvement. The patients with pre-MR grades 2-4 and improved MR after CRT showed significantly better prognosis in heart failure hospitalization. Cutoff values of ≥ 19.5 ms of the reduction of TD_late-inf and ≥ 30.8% of the %reduction of LVESV were significantly associated with the decrease in heart failure hospitalization. The improved interpapillary muscle activation time delay and volume reduction after CRT were associated with acute and late MR improvements. There may be different time course of recovery and distinct causes for late MR improvement.

Regional Strain Pattern Index-A Novel Technique to Predict CRT Response

Background: Cardiac resynchronization therapy (CRT) improves outcome in patients with heart failure (HF) however approximately 30% of patients still remain non-responsive. We propose a novel index—Regional Strain Pattern Index (RSPI)—to prospectively evaluate response to CRT. Methods: Echocardiography was performed in 49 patients with HF (66.5 ± 10 years, LVEF 24.9 ± 6.4%, QRS width 173.1 ± 19.1 ms) two times: before CRT implantation and 15 ± 7 months after. At baseline, dyssynchrony was assessed including RSPI and strain pattern. RSPI was calculated from all three apical views across 12 segments as the sum of dyssynchronous components. From every apical view, presence of four components were assessed: (1) contraction of the early-activated wall; (2) prestretching of the late activated wall; (3) contraction of the early-activated wall in the first 70% of the systolic ejection phase; (4) peak contraction of the late-activated wall after aortic valve closure. Each component scored 1 point, thus the maximum was 12 points. Results: Responders reached higher mean RSPI values than non-responders (5.86 ± 2.9 vs. 4.08 ± 2.4; p = 0.044). In logistic regression analysis value of RSPI ≥ 7 points was a predictor of favorable CRT effect (OR: 12; 95% CI = 1.33–108.17; p = 0.004). Conclusions: RSPI could be a valuable predictor of positive outcome in HF patients treated with CRT.

Importance of Systematic Right Ventricular Assessment in Cardiac Resynchronization Therapy Candidates: A Machine Learning Approach

BACKGROUND

Despite all having systolic heart failure and broad QRS intervals, patients screened for cardiac resynchronization therapy (CRT) are highly heterogeneous, and it remains extremely challenging to predict the impact of CRT devices on left ventricular function and outcomes. The aim of this study was to evaluate the relative impact of clinical, electrocardiographic, and echocardiographic data on the left ventricular remodeling and prognosis of CRT candidates by the application of machine learning approaches.

METHODS

One hundred ninety-three patients with systolic heart failure receiving CRT according to current recommendations were prospectively included in this multicenter study. A combination of the Boruta algorithm and random forest methods was used to identify features predicting both CRT volumetric response and prognosis. Model performance was tested using the area under the receiver operating characteristic curve. The k-medoid method was also applied to identify clusters of phenotypically similar patients.

RESULTS

From 28 clinical, electrocardiographic, and echocardiographic variables, 16 features were predictive of CRT response, and 11 features were predictive of prognosis. Among the predictors of CRT response, eight variables (50%) pertained to right ventricular size or function. Tricuspid annular plane systolic excursion was the main feature associated with prognosis. The selected features were associated with particularly good prediction of both CRT response (area under the curve, 0.81; 95% CI, 0.74-0.87) and outcomes (area under the curve, 0.84; 95% CI, 0.75-0.93). An unsupervised machine learning approach allowed the identification of two phenogroups of patients who differed significantly in clinical variables and parameters of biventricular size and right ventricular function. The two phenogroups had significantly different prognosis (hazard ratio, 4.70; 95% CI, 2.1-10.0; P < .0001; log-rank P < .0001).

CONCLUSIONS

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

Multimodality imaging in the diagnosis, risk stratification, and management of patients with dilated cardiomyopathies: an expert consensus document from the European Association of Cardiovascular Imaging

Dilated cardiomyopathy (DCM) is defined by the presence of left ventricular or biventricular dilatation and systolic dysfunction in the absence of abnormal loading conditions or coronary artery disease sufficient to explain these changes. This is a heterogeneous disease frequently having a genetic background. Imaging is important for the diagnosis, the prognostic assessment and for guiding therapy. A multimodality imaging approach provides a comprehensive evaluation of all the issues related to this disease. The present document aims to provide recommendations for the use of multimodality imaging according to the clinical question. Selection of one or another imaging technique should be based on the clinical condition and context. Techniques are presented with the aim to underscore what is 'clinically relevant' and what are the tools that 'can be used'. There remain some gaps in evidence on the impact of multimodality imaging on the management and the treatment of DCM patients where ongoing research is important.

Left Bundle Branch Pacing: A New Alternative to Resynchronization Therapy in the 2020 Pacing Armamentarium

His bundle pacing was developed while seeking a physiological alternative to biventricular cardiac resynchronization therapy. However, His bundle pacing may not be adequate in all patients. In this scenario, left bundle branch pacing has arisen as a new cardiac resynchronization therapy modality to correct left bundle branch block and restore ventricular synchrony. (Level of Difficulty: Intermediate.).

Interpretable Deep Models for Cardiac Resynchronisation Therapy Response Prediction

Advances in deep learning (DL) have resulted in impressive accuracy in some medical image classification tasks, but often deep models lack interpretability. The ability of these models to explain their decisions is important for fostering clinical trust and facilitating clinical translation. Furthermore, for many problems in medicine there is a wealth of existing clinical knowledge to draw upon, which may be useful in generating explanations, but it is not obvious how this knowledge can be encoded into DL models - most models are learnt either from scratch or using transfer learning from a different domain. In this paper we address both of these issues. We propose a novel DL framework for image-based classification based on a variational autoencoder (VAE). The framework allows prediction of the output of interest from the latent space of the autoencoder, as well as visualisation (in the image domain) of the effects of crossing the decision boundary, thus enhancing the interpretability of the classifier. Our key contribution is that the VAE disentangles the latent space based on 'explanations' drawn from existing clinical knowledge. The framework can predict outputs as well as explanations for these outputs, and also raises the possibility of discovering new biomarkers that are separate (or disentangled) from the existing knowledge. We demonstrate our framework on the problem of predicting response of patients with cardiomyopathy to cardiac resynchronization therapy (CRT) from cine cardiac magnetic resonance images. The sensitivity and specificity of the proposed model on the task of CRT response prediction are 88.43% and 84.39% respectively, and we showcase the potential of our model in enhancing understanding of the factors contributing to 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.

Variability in the Assessment of Myocardial Strain Patterns: Implications for Adequate Interpretation

Variability in global and regional peak strain has been thoroughly studied, but variability in spatiotemporal myocardial strain patterns has not been studied as well. This study reports on such variability and its implications for adequate disease interpretation. Forty in-training operators, distributed on 20 workstations, analyzed six cases with representative deformation patterns with commercial speckle tracking. Inter-operator differences were quantified through the variability in myocardial delineations, spatiotemporal longitudinal strain patterns and peak longitudinal strain. Intra-operator differences were assessed similarly using 10 repeated measurements from a single clinician expert. Delineations varied mainly along the lateral wall and at the valve level. Peak longitudinal strain variability was low to moderate. The spatiotemporal strain patterns were consistent despite high variability at the apex and near the valve. The results indicate that relevant pattern assessment is possible despite heterogeneous experience with speckle tracking and that careful interpretation of pattern abnormalities should be recommended before a more systematic quantitative analysis.

Myocardial work is a predictor of exercise tolerance in patients with dilated cardiomyopathy and left ventricular dyssynchrony

The assessment of myocardial work (MW) by pressure-strain loops is a recently introduced tool for the assessment of myocardial performance. Aim of the present study is to evaluate the relationship between myocardial work and exercise tolerance in patients with dilated cardiomyopathy (DCM). 51 patients with DCM (mean age 57 ± 13 years, left ventricular ejection fraction: 32 ± 9%) underwent cardiopulmonary exercise test (CPET) to assess exercise performance. 22 patients (43%) had left or right bundle branch block with QRS duration > 120 ms. Trans-thoracic echocardiography (TTE) was performed before CPET. The following indices of myocardial work (MW) were measured regionally and globally: constructive work (CW), wasted work (WW), and work efficiency (WE). Left ventricular dyssynchrony (LV-DYS) was defined by the presence of septal flash or apical rocking at TTE. LV-DYS was observed in 16 (31%) patients and associated with lower LV ejection fraction (LVEF), lower global and septal WE, and higher global and septal WW. In patients with LV-DYS, septal WE was the only predictor of exercise capacity at multivariable analysis (β = 0.68, p = 0.03), whereas LVEF (β = 0.47, p = 0.05) and age (β = - 0.42, p = 0.04) were predictors of exercise capacity in patients without LV-DYS. In patients with DCM, LV-DYS is associated with an heterogeneous distribution of myocardial work. Septal WE is the best predictor of exercise performance in these patients.