Fusion-Optimized Intervals (FOI): A New Method to Achieve the Narrowest QRS for Optimization of the AV and VV Intervals in Patients Undergoing Cardiac Resynchronization Therapy

Emergent role of dynamic optimization in cardiac resynchronization therapy: Systematic review and network meta-analysis

AIMS

Suboptimal device programming is frequent in non-responders to cardiac resynchronization therapy (CRT). However, the role of device optimization and the most appropriate technique are still unknown. The aim of our study was to analyse the effect of different CRT optimization techniques within a network meta-analysis.

METHODS

A systematic search was conducted on MEDLINE, Embase and CENTRAL for studies comparing outcomes with empirical device settings or optimization using echocardiography, static algorithms or dynamic algorithms. Studies investigating the effect of optimization in non-responders were also analysed.

RESULTS

A total of 17 studies with 4346 patients were included in the quantitative analysis. Of the treatments and outcomes examined, a significant difference was found only between dynamic algorithms and echocardiography, with the former leading to a higher echocardiographic response rate [odds ratio (OR): 2.02, 95% confidence interval (CI) 1.21-3.35], lower heart failure hospitalization rate (OR: 0.75, 95% CI 0.57-0.99) and greater improvement in 6-minute walk test [mean difference (MD): 45.52 m, 95% credible interval (CrI) 3.91-82.44 m]. We found no significant difference between empirical settings, static algorithms and dynamic algorithms. Seven studies with 228 patients reported response rates after optimization in non-responders. Altogether, 34.3%-66.7% of initial non-responders showed improvement after optimization, depending on response criteria.

CONCLUSIONS

At the time of CRT implantation, dynamic algorithms may serve as a resource-friendly alternative to echocardiographic optimization, with similar or better mid-term outcomes. However, their superiority over empirical device settings needs to be investigated in further trials. For non-responders, CRT optimization should be considered, as the majority of patients experience improvement.

Pilot study to evaluate left-to-right ventricular offset in biventricular pacing-comparison of electrocardiographic imaging and ECG

INTRODUCTION

Biventricular pacing (BiVp) improves outcomes in systolic heart failure patients with electrical dyssynchrony. BiVp is delivered from epicardial left ventricular (LV) and endocardial right ventricular (RV) electrodes. Acute electrical activation changes with different LV-RV stimulation offsets can help guide individually optimized BiVp programming. We sought to study the BiVp ventricular activation with different LV-RV offsets and compare with 12-lead ECG.

METHODS

In five patients with BiVp (63 ± 17-year-old, 80% male, LV ejection fraction 27 ± 6%), we evaluated acute ventricular epicardial activation, varying LV-RV offsets in 20 ms increments from -40 to 80 ms, using electrocardiographic imaging (ECGI) to obtain absolute ventricular electrical uncoupling (VEUabs, absolute difference in average LV and average RV activation time) and total activation time (TAT). For each patient, we calculated the correlation between ECGI and corresponding ECG (3D-QRS-area and QRS duration) with different LV-RV offsets.

RESULTS

The LV-RV offset to attain minimum VEUabs in individual patients ranged 20-60 ms. In all patients, a larger LV-RV offset was required to achieve minimum VEUabs (36 ± 17 ms) or 3D-QRS-area (40 ± 14 ms) than that for minimum TAT (-4 ± 9 ms) or QRS duration (-8 ± 11 ms). In individual patients, 3D-QRS-area correlated with VEUabs (r 0.65 ± 0.24) and QRS duration correlated with TAT (r 0.95 ± 0.02). Minimum VEUabs and minimum 3D-QRS-area were obtained by LV-RV offset within 20 ms of each other in all five patients.

CONCLUSIONS

LV-RV electrical uncoupling, as assessed by ECGI, can be minimized by optimizing LV-RV stimulation offset. 3D-QRS-area is a surrogate to identify LV-RV offset that minimizes LV-RV uncoupling.

Association between QRS shortening and mortality after cardiac resynchronization therapy: Results from the DANISH study

BACKGROUND

Changes in QRS duration (∆QRS) are often used in the clinical setting to evaluate the effect of cardiac resynchronization therapy (CRT), although an association between ∆QRS and outcomes is not firmly established. We aimed to assess the association between mortality and ∆QRS after CRT in patients from the DANISH (Danish Study to Assess the Efficacy of ICDs in Patients with Non-Ischemic Systolic Heart Failure on Mortality) study.

METHODS

We included all patients from DANISH who received a CRT device and had available QRS duration data before and after implantation. Cox proportional hazards models were used to assess associations between ∆QRS (post-CRT QRS minus pre-CRT QRS) and mortality.

RESULTS

Complete data were available in 572 patients. Median baseline QRS duration was 160 ms (IQR [146;180]). Post-CRT QRS was recorded a median of 48 days (IQR [33;86]) after implantation, and the median ∆QRS was -14 ms (IQR [-38;-3]). During a median follow-up of 4.1 years (IQR [2.5;5.8]), 106 patients died. In crude Cox regression, all-cause mortality was reduced by 6% per 10 ms shortening of QRS (HR 0.94; CI: 0.88-1.00, p = 0.04). The effect did not remain significant after multivariable adjustment (HR 1.01, CI: 0.93-1.10, p = 0.77). Further, no association was found between ∆QRS and improvement of New York Heart Association functional class at 6 months (OR 1.03, CI: 0.96-1.10, p = 0.42).

CONCLUSION

In a large cohort of patients with non-ischemic cardiomyopathy, reduction of QRS duration after CRT was not associated with changes in mortality during long-term follow-up.

Predictors for Super-Responders in Cardiac Resynchronization Therapy

BACKGROUND

Prediction of cardiac resynchronization therapy (CRT) response, particularly a super-response, is of great importance.

STUDY QUESTION

The aim of our study was to assess the predictors for super-responders in CRT.

STUDY DESIGN

We conducted a retrospective, observational study, which finally included 622 patients with heart failure treated with CRT between January 2008 and May 2020 who had a minimal follow-up of 6 months after CRT.

MEASURES AND OUTCOMES

A total of 192 super-responders, defined by a left ventricular ejection fraction (LVEF) of at least 45%, and/or minimum 15% increase in LVEF and an improvement of the New York Heart Association functional class by at least 2 degrees at the last follow-up, and the rest of 430 patients who did not fulfill the super-responder criteria.

RESULTS

The highest rate of super-responders (41.91%, n = 171) was at patients with left ventricle-only pacing with optimal fusion (OPT) compared with patients with biventricular (BiV) pacing (9.81%, n = 21, P < 0.000). In the OPT group, univariable analysis showed that nonischemic cardiomyopathy, a smaller degree of mitral regurgitation, and better left ventricle function at enrollment were predictors for super-response compared with the BiV group where a narrower QRS after implantation, nonischemic cardiomyopathy, and a better baseline LVEF were predictors for super-responders. In the multivariable analysis, both narrower QRS after implantation and nonischemic cardiomyopathy were independent predictors for super-response in the BiV group compared with OPT where nonischemic cardiomyopathy remained the only independent predictor for super-response.

CONCLUSIONS

In this retrospective study, OPT CRT programing was an additional predictor of super-response to CRT besides nonischemic cardiomyopathy.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

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.

Visualization of the SyncAV® Algorithm for CRT Optimization by Non-invasive Imaging of Cardiac Electrophysiology: NICE-CRT Trial

(1) Background: Periodic repetitive AV interval optimization using a device-based algorithm in cardiac resynchronization therapy (CRT) devices may improve clinical outcomes. There is an unmet need to successfully transform its application into clinical routine. (2) Methods: Non-invasive imaging of cardiac electrophysiology was performed in different device programming settings of the SyncAV^® algorithm in 14 heart failure patients with left bundle branch block and a PR interval ≤ 250 milliseconds to determine the shortest ventricular activation time. (3) Results: the best offset time (to be manually programmed) permitting automatic dynamic adjustment of the paced atrioventricular interval after every 256 heart beats was found to be 30 and 50 milliseconds, decreasing mean native QRS duration from 181.6 ± 23.9 milliseconds to 130.7 ± 10.0 and 130.1 ± 10.5 milliseconds, respectively (p = 0.01); this was followed by an offset of 40 milliseconds (decreasing QRS duration to 130.1 ± 12.2 milliseconds; p = 0.08). (4) Conclusions: The herein presented NICE-CRT study supports the current recommendation to program an offset of 50 milliseconds as default in patients with left bundle branch block and preserved atrioventricular conduction after implantation of a CRT device capable of SyncAV^® optimization. Alternatively, offset programming of 30 milliseconds may also be applied as default programming. In patients with no or poor CRT response, additional efforts should be spent to individualize best offset programming with electrocardiographic optimization techniques.

Stepwise application of ECG and electrogram-based criteria to ensure electrical resynchronization with left bundle branch pacing

AIMS

To define a stepwise application of left bundle branch pacing (LBBP) criteria that will simplify implantation and guarantee electrical resynchronization. Left bundle branch pacing has emerged as an alternative to biventricular pacing. However, a systematic stepwise criterion to ensure electrical resynchronization is lacking.

METHODS AND RESULTS

A cohort of 24 patients from the LEVEL-AT trial (NCT04054895) who received LBBP and had electrocardiographic imaging (ECGI) at 45 days post-implant were included. The usefulness of ECG- and electrogram-based criteria to predict accurate electrical resynchronization with LBBP were analyzed. A two-step approach was developed. The gold standard used to confirm resynchronization was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. Twenty-two (91.6%) patients showed electrical resynchronization on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120 ms) resulted in 95% sensitivity and 100% specificity to predict LBBP resynchronization, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R <80 ms in non-selective capture (100% specificity, sensitivity 46%) ensured 100% accuracy to predict resynchronization with LBBP.

CONCLUSION

Stepwise application of ECG and electrogram criteria may provide an accurate assessment of electrical resynchronization with LBBP (Graphical abstract).

Conduction System Pacing vs Biventricular Pacing in Heart Failure and Wide QRS Patients: LEVEL-AT Trial

BACKGROUND

Conduction system pacing (CSP) has emerged as an alternative to biventricular pacing (BiVP). Randomized studies comparing both therapies are scarce and do not include left bundle branch pacing.

OBJECTIVES

This study aims to compare ventricular resynchronization achieved by CSP vs BiVP in patients with cardiac resynchronization therapy indication.

METHODS

LEVEL-AT (Left Ventricular Activation Time Shortening with Conduction System Pacing vs Biventricular Resynchronization Therapy) was a randomized, parallel, controlled, noninferiority trial. Seventy patients with cardiac resynchronization therapy indication were randomized 1:1 to BiVP or CSP, and followed up for 6 months. Crossover was allowed when primary allocation procedure failed. Primary endpoint was the change in left ventricular activation time, measured using electrocardiographic imaging. Secondary endpoints were left ventricular reverse remodeling and the combined endpoint of heart failure hospitalization or death at 6-month follow-up.

RESULTS

Thirty-five patients were allocated to each group. Eight (23%) patients crossed over from CSP to BiVP; 2 patients (6%) crossed over from BiVP to CSP. Electrocardiographic imaging could not be performed in 2 patients in each group. A similar decrease in left ventricular activation time was achieved by CSP and BiVP (-28 ± 26 ms vs -21 ± 20 ms, respectively; mean difference -6.8 ms; 95% CI: -18.3 ms to 4.6 ms; P < 0.001 for noninferiority). Both groups showed a similar change in left ventricular end-systolic volume (-37 ± 59 mL CSP vs -30 ± 41 mL BiVP; mean difference: -8 mL; 95% CI: -33 mL to 17 mL; P = 0.04 for noninferiority) and similar rates of mortality or heart failure hospitalizations (2.9% vs 11.4%, respectively) (P = 0.002 for noninferiority).

CONCLUSIONS

Similar degrees of cardiac resynchronization, ventricular reverse remodeling, and clinical outcomes were attained by CSP as compared to BiVP. CSP could be a feasible alternative to BiVP. (LEVEL-AT [Left Ventricular Activation Time Shortening With Conduction System Pacing vs Biventricular Resynchronization Therapy]; NCT04054895).

What Have We Learned in the Last 20 Years About CRT Non-Responders?

Although cardiac resynchronization therapy (CRT) has become well established in the treatment of heart failure, the management of patients who do not respond after CRT remains a key challenge. This review will summarize what we have learned about non-responders over the last 20 years and discuss methods for optimizing response, including the introduction of novel therapies.

Programming Algorithms for Cardiac Resynchronization Therapy

Current cardiac resynchronization therapy (CRT) implant guidelines emphasize the presence of electrical dyssynchrony (left bundle branch block (LBBB) and QRS > 150 ms) yet have modest predictive value for response and have not reduced the 30% nonresponse rate. Optimized programming to optimize CRT delivery has promised much but to date has largely been ineffective. What is missing is the understanding of LV paced effects (which are unpredictable) and optimal paced AV interval (that can be conserved during physiologic variations) that then can be incorporated into an individualized programming prescription. Automatic device-based algorithms that deliver electrical optimization and maintain this during ambulatory fluctuations in AV interval are discussed.

His-Optimized and Left Bundle Branch-Optimized Cardiac Resynchronization Therapy: In Control of Fusion Pacing

Fusion pacing, which exploits conduction via the intrinsic His-Purkinje system, forms the basis of recent cardiac resynchronization therapy (CRT) optimization algorithms. However, settings need to be constantly adjusted to accommodate for changes in AV conduction, and the algorithms are not always available (eg, depending on the device, in case of AV block or with atrial fibrillation). His-optimized cardiac resynchronization therapy (HOT-CRT), and left-bundle branch optimized cardiac resynchronization therapy (LOT-CRT) which combines conduction system pacing with ventricular fusion pacing, provide constant fusion with ventricular activation (irrespective of intrinsic AV conduction). These modalities provide promising treatment strategies for patients with heart failure, especially in those with chronic atrial fibrillation who require CRT (in whom the atrial port is usually plugged and can be used to connect the conduction system pacing lead).

Betablockers and Ivabradine Titration According to Exercise Test in LV Only Fusion CRT Pacing

Background: Betablockers (BB)/ivabradine titration in fusion CRT pacing (CRTP) is understudied. Aim: To assess drug optimization using systematic exercise tests (ET) in fusion CRTP with preserved atrioventricular conduction (AVc). Methods: Changes in drug management were assessed during systematic follow-ups in CRTP patients without right ventricle lead. Shorter AVc (PR interval) allowed BB up-titration, while longer AVc needed BB down-titration, favoring ivabradine. Constant fusion pacing was the goal to improve outcomes. Results: 64 patients, 62.5 ± 9.5 y.o divided into three groups: shorter PR (<160 ms), normal (160−200 ms), longer (200−240 ms); follow-up 59 ± 26 months. Drugs were titrated in case of: capture loss due to AVc shortening (14%), AVc lengthening (5%), chronotropic incompetence (11%), maximum tracking rate issues (9%), brady/tachyarrhythmias (8%). Interventions: BB up-titration (78% shorter PR, 19% normal PR, 5% longer PR), BB down-titration (22% shorter PR, 14% normal PR), BB exclusion (16% longer PR), adding/up-titration ivabradine (22% shorter PR, 19% normal PR, 5% longer PR), ivabradine down-titration (22% shorter PR, 3% normal PR), ivabradine exclusion (11% normal PR, 5% longer PR). Drug strategy was changed in 165 follow-ups from 371 recorded (42% patients). Conclusions: BBs/ivabradine titration and routine ET during follow-ups in patients with fusion CRTP should be a standard approach to maximize resynchronization response. Fusion CRTP showed a positive outcome with important LV reverse remodeling and significant LVEF improvement in carefully selected patients.

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.

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.

Electrocardiography of cardiac resynchronization therapy: Pitfalls and practical tips

Cardiac resynchronization therapy (CRT) has been established as an effective mode of therapy in patients with heart failure and concurrent cardiac dyssynchrony, principally in the form of left bundle branch block (LBBB). The widespread use of CRT has ushered in a new landscape in 12-lead electrocardiography (ECG). ECG readings in these patients are most important to guide troubleshooting and also appropriate device programming, as well as discerning and managing nonresponders. A set of four ECG recordings need to accompany each patient with a CRT device, including a baseline ECG and recordings from monochamber (right and left ventricular) and biventricular pacing, which can be compared against a new recording to facilitate the evaluation of proper versus problematic biventricular pacing. Precordial ECG leads V1/2 acquired at the fourth intercostal space and limb leads, I and III, together with a quick assessment of perpendicular leads I and aVF to determine the quadrant of the QRS axis in the hexaxial diagram, may provide the framework for proper ECG interpretation in these patients. This important issue of 12-lead ECG in CRT patients is herein reviewed, pitfalls are pointed out and practical tips are provided for ECG reading to help recognize and manage problems with CRT device function. Furthermore, several pertinent ECG recordings and tabulated data are provided, and an algorithm is suggested that integrates prior algorithms and relevant information from current literature.

Improvement of LV Reverse Remodeling Using Dynamic Programming of Fusion-Optimized Atrioventricular Intervals in Cardiac Resynchronization Therapy

Background: The patient-tailored SyncAV algorithm shortens the QRS duration (QRSd) beyond what conventional biventricular (BiV) pacing can. However, evidence of the ability of SyncAV to improve the cardiac resynchronization therapy (CRT) response is lacking. The aim of this study was to evaluate the impact of CRT enhanced by SyncAV on echocardiographic and clinical responses.

Methods and Results: Consecutive heart failure (HF) patients from three centers treated with a quadripolar CRT system (Abbott) were enrolled. The total of 122 patients were divided into BiV+SyncAV (n = 68) and BiV groups (n = 54) according to whether they underwent CRT with or without SyncAV. Electrocardiographic, echocardiographic, and clinical data were assessed at baseline and during follow-up. Echocardiographic response to CRT was defined as a ≥15% decrease in left ventricular end-systolic volume (LVESV), and clinical response was defined as a NYHA class reduction of ≥1. At the 6-month follow-up, the baseline QRSd and LVESV decreased more significantly in the BiV+SyncAV than in the BiV group (QRSd −36.25 ± 16.33 vs. −22.72 ± 18.75 ms, P < 0.001; LVESV −54.19 ± 38.87 vs. −25.37 ± 36.48 ml, P < 0.001). Compared to the BiV group, more patients in the BiV+SyncAV group were classified as echocardiographic (82.35 vs. 64.81%; P = 0.036) and clinical responders (83.82 vs. 66.67%; P = 0.033). During follow-up, no deaths due to HF deterioration or severe procedure related complications occurred.

Conclusion: Compared to BiV pacing, BiV combined with SyncAV leads to a more significant reduction in QRSd and improves LV remodeling and long-term outcomes in HF patients treated with CRT.

Fusion Pacing with Biventricular, Left Ventricular-only and Multipoint Pacing in Cardiac Resynchronisation Therapy: Latest Evidence and Strategies for Use

Despite advances in the field of cardiac resynchronisation therapy (CRT), response rates and durability of therapy remain relatively static. Optimising device timing intervals may be the most common modifiable factor influencing CRT efficacy after implantation. This review addresses the concept of fusion pacing as a method for improving patient outcomes with CRT. Fusion pacing describes the delivery of CRT pacing with a programming strategy to preserve intrinsic atrioventricular (AV) conduction and ventricular activation via the right bundle branch. Several methods have been assessed to achieve fusion pacing. QRS complex duration (QRSd) shortening with CRT is associated with improved clinical response. Dynamic algorithm-based optimisation targeting narrowest QRSd in patients with intact AV conduction has shown promise in people with heart failure with left bundle branch block. Individualised dynamic programming achieving fusion may achieve the greatest magnitude of electrical synchrony, measured by QRSd narrowing.

Cardiac Resynchronization Therapy Response Is Equalized in Men and Women by Electrical Optimization: PR Matters

OBJECTIVES

This study hypothesized that the shorter intrinsic PR interval observed in women allows a greater degree of fusion with intrinsic conduction, achieving a shorter QRS interval duration and, thus, a better response.

BACKGROUND

Women benefit more from cardiac resynchronization therapy (CRT) than men. However, the reason for this difference remains elusive.

METHODS

A cohort of 180 patients included in the BEST (Fusion based optimization in resynchronization therapy [ECG Optimization of CRT: Evaluation of Mid-Term Response]; NCT01439529) study were retrospectively analyzed. Patients were initially randomized to either nonoptimized CRT (NON-OPT group; n = 89) or electrocardiographically optimized CRT based on the fusion-optimized intervals (FOI) method (FOI group; n = 91). Echocardiographic response was defined as a >15% decrease in left ventricular end-systolic volume at the 12-month follow-up.

RESULTS

The basal PR interval was shorter in women as compared to men. In the NON-OPT group, CRT resulted in a shorter paced QRS interval in women than in men (134 ± 21 ms vs. 151 ± 21 ms, respectively; p = 0.003, 95% confidence interval [CI]: -27 to -5.6) and better response in women than in men: 70.4% vs. 46.4%, respectively (odds ratio: 0.37; p = 0.04; 95% CI: 0.14 to 0.97). There were no differences in paced QRS interval duration (126 ± 13 ms vs. 129 ± 17 ms; p = 0.47) or response between women and men in the FOI group (68% vs. 70.5%; odds ratio: 1.12; p = 0.82; 95% CI: 0.41 to 3.07). FOI extended the atrioventricular interval to obtain the best fusion; the atrioventricular intervals tended to require greater extension in men than in women (22 ± 33 ms vs. 8 ± 28 ms, respectively; p = 0.07).

CONCLUSIONS

Women had a shorter PR interval, which was associated with a shorter QRS interval and better response to CRT. The difference in QRS interval duration and response between men and women did not persist when CRT was optimized using fusion with intrinsic conduction (FOI programming).

An electrographic AV optimization for the maximum integrative atrioventricular and ventricular resynchronization in CRT

BACKGROUND

Atrioventricular (AV) delay could affect AV and ventricular synchrony in cardiac resynchronization therapy (CRT). Strategies to optimize AV delay according to optimal AV synchrony (AV_opt-AV) or ventricular synchrony (AV_opt-V) would potentially be discordant. This study aimed to explore a new AV delay optimization algorithm guided by electrograms to obtain the maximum integrative effects of AV and ventricular resynchronization (opt-AV).

METHODS

Forty-nine patients with CRT were enrolled. AV_opt-AV was measured through the Ritter method. AV_opt-V was obtained by yielding the narrowest QRS. The opt-AV was considered to be AV_opt-AV or AV_opt-V when their difference was < 20 ms, and to be the AV delay with the maximal aortic velocity-time integral between AV_opt-AV and AV_opt-V when their difference was > 20 ms.

RESULTS

The results showed that sensing/pacing AV_opt-AV (SAV_opt-AV/PAV_opt-AV) were correlated with atrial activation time (P_end-As/P_end-Ap) (P < 0.05). Sensing/pacing AV_opt-V (SAV_opt-V/PAV_opt-V) was correlated with the intrinsic AV conduction time (As-Vs/Ap-Vs) (P < 0.01). The percentages of patients with more than 20 ms differences between SAV_opt-AV/PAV_opt-AV and SAV_opt-V/PAV_opt-V were 62.9% and 57.1%, respectively. Among them, opt-AV was linearly correlated with SAV_opt-AV/PAV_opt-AV and SAV_opt-V/PAV_opt-V. The sensing opt-AV (opt-SAV) = 0.1 × SAV_opt-AV + 0.4 × SAV_opt-V + 70 ms (R² = 0.665, P < 0.01) and the pacing opt-AV (opt-PAV) = 0.25 × PAV_opt-AV + 0.5 × PAV_opt-V + 30 ms (R² = 0.560, P < 0.01).

CONCLUSION

The SAV_opt-AV/PAV_opt-AV and SAV_opt-V/PAV_opt-V were correlated with the atrial activation time and the intrinsic AV conduction interval respectively. Almost half of the patients had a > 20 ms difference between SAV_opt-AV/PAV_opt-AV and SAV_opt-V/PAV_opt-V. The opt-AV could be estimated based on electrogram parameters.

Determinants of LV dP/dtmax and QRS duration with different fusion strategies in cardiac resynchronisation therapy

BACKGROUND

We designed this study to assess the acute effects of different fusion strategies and left ventricular (LV) pre-excitation/post-excitation on LV dP/dtmax and QRS duration (QRSd).

METHODS

We measured LV dP/dtmax and QRSd in 19 patients having cardiac resynchronisation therapy (CRT). Two groups of biventricular pacing were compared: pacing the left ventricle (LV) with FUSION with intrinsic right ventricle (RV) activation (FUSION), and pacing the LV and RV with NO FUSION with intrinsic RV activation. In the NO FUSION group, the RV was paced before the expected QRS onset. A quadripolar LV lead enabled distal, proximal and multipoint pacing (MPP). The LV was stimulated relative in time to either RV pace or QRS-onset in four pre-excitation/post-excitation classes (PCs). We analysed the interactions of two groups (FUSION/NO FUSION) with three different electrode configurations, each paced with four different degrees of LV pre-excitation (PC1-4) in a statistical model.

RESULTS

LV dP/dtmax was higher with NO FUSION than with FUSION (769±46 mm Hg/s vs 746±46 mm Hg/s, p<0.01), while there was no difference in QRSd (NO FUSION 156±2 ms and FUSION 155±2 ms). LV dP/dtmax and QRSd increased with LV pre-excitation compared with pacing timed to QRS/RV pace-onset regardless of electrode configuration. Overall, pacing LV close to QRS-onset (FUSION) with MPP shortened QRSd the most, while LV dP/dtmax increased the most with LV pre-excitation.

CONCLUSION

We show how a beneficial change in QRSd dissociates from the haemodynamic change in LV dP/dtmax with different biventricular pacing strategies. In this study, LV pre-excitation was the main determinant of LV dP/dtmax, while QRSd shortens with optimal resynchronisation.

Cardiac Resynchronization Therapy in Patients with Heart Failure: What is New?

Cardiac resynchronization therapy (CRT) is an established treatment of patients with medically refractory, mild-to-severe systolic heart failure (HF), impaired left ventricular function, and wide QRS complex. The pathologic activation sequence observed in patients with abnormal QRS duration and morphology results in a dyssynchronous ventricular activation and contraction leading to cardiac remodeling, worsening systolic and diastolic function, and progressive HF. In this article, the authors aim to explore the current CRT literature, focusing their attentions on the promising innovation in this field.

Optimized single-point left ventricular pacing leads to improved resynchronization compared with multipoint pacing

BACKGROUND

Multipoint pacing (MPP) in cardiac resynchronization therapy (CRT) activates the left ventricle from two locations, thereby shortening the QRS duration and enabling better resynchronization; however, compared with conventional CRT, MPP reduces battery longevity. On the other hand, electrocardiogram-based optimization using the fusion-optimized intervals (FOI) method achieves more significant reverse remodeling than nominal CRT programming. Our study aimed to determine whether MPP could attain better resynchronization than single-point pacing (SPP) optimized by FOI.

METHODS

This prospective study included 32 consecutive patients who successfully received CRT devices with MPP capabilities. After implantation, the QRS duration was measured during intrinsic rhythm and with three pacing configurations: MPP, SPP-FOI, and MPP-FOI. In 14 patients, biventricular activation times (by electrocardiographic imaging, ECGI) were obtained during intrinsic rhythm and for each pacing configuration to validate the findings. Device battery longevity was estimated at the 45-day follow-up.

RESULTS

The SPP-FOI method achieved greater QRS shortening than MPP (-56 ± 16 vs. -42 ± 17 ms, p < .001). Adding MPP to the best FOI programming did not result in further shortening (MPP-FOI: -58 ± 14 ms, p = .69). Although biventricular activation times did not differ significantly among the three pacing configurations, only the two FOI configurations achieved significant shortening compared with intrinsic rhythm. The estimated battery longevity was longer with SPP than with MPP (8.1 ± 2.3 vs. 6.3 ± 2.0 years, p = .03).

CONCLUSIONS

SPP optimized by FOI resulted in better resynchronization and longer battery duration than MPP.

Impact of synchronous atrioventricular delay optimization on left ventricle flow force angle evaluated by echocardiographic particle image velocimetry

PURPOSE

To evaluate the improvement in electrical synchrony and left ventricle (LV) hemodynamics provided by combining the dynamic atrioventricular delay (AVD) of SyncAV^TM CRT and the multiple LV pacing sites of MultiPoint pacing (MPP).

METHODS

Patients with LBBB and QRS duration (QRSd) > 140 ms implanted with a CRT-D or CRT-P device and quadripolar LV lead were enrolled in this prospective study. During a post-implant follow-up visit, QRSd was measured from 12-lead surface electrograms by experts blinded to pacing configurations. QRSd reduction relative to intrinsic rhythm was evaluated during biventricular pacing (BiV) and MPP for two AVDs: nominal (140/110 ms paced/sensed) and SyncAV (patient-optimized SyncAV offset [10-60 ms] minimizing QRSd). Echocardiography particle imaging velocimetry (Echo-PIV) analysis was performed for each configuration. The resulting hemodynamic force LV flow angle (φ) was analyzed, which ranges from 0^o (predominantly base-apex forces) to 90^o (predominantly transverse forces). Higher angles indicate more energy dissipation at lateral walls due to transverse flow; lower angles indicate healthier flow aligned with the longitudinal base-apex path of the pressure gradient.

RESULTS

Twelve patients (58% male, 17% ischemic, 32±7% ejection fraction, 165 ± 18 ms intrinsic QRSd) completed QRSd and Echo-PIV assessment. Relative to intrinsic rhythm, BiV and MPP with nominal AVD reduced QRSd by 10 ± 9% and 12 ± 9%, respectively. BiV+SyncAV and MPP+SyncAV further reduced QRSd by 19 ± 8%, (p < 0.05 vs. BiV with nominal AVD) and 23 ± 9% (p < 0.05 vs BiV+SyncAV), respectively. Echo-PIV showed similar sequential hemodynamic improvements. LV flow angular orientation during intrinsic activation (46 ± 3^o) reduced with BiV+SyncAV (37 ± 4^o, p < 0.05 vs intrinsic) and further with MPP+SyncAV (34 ± 4^o, p < 0.05 vs BiV+SyncAV).

CONCLUSION

These results suggest that SyncAV may improve electrical synchrony and influence LV flow patterns in patients suffering from heart failure compared to conventional CRT with a fixed AVD, with further improvement observed by combining with MPP.

Impact of QRS morphology on response to conduction system pacing after atrioventricular junction ablation

Aims

His–Purkinje conduction system pacing (HPCSP) utilizing His (HBP) or left bundle branch pacing (LBBP) in patients with atrial fibrillation (AF) and wide QRS duration has not been well studied. We assessed the benefit of left bundle branch block (LBBB) correction during HPCSP in AF patients undergoing atrioventricular junction (AVJ) ablation with LBBB, compared with those with narrow QRS duration.

Methods and results

This is an observational study in consecutive patients with typical LBBB or narrow QRS duration in whom we attempted HPCSP after AVJ ablation for refractory AF with a left ventricular ejection fraction (LVEF) ≤ 50%. Echocardiographic responses and clinical outcomes were assessed at baseline and during 1 year of follow‐up. A total of 178 patients were enrolled, of which 170 achieved AVJ ablation + permanent HPCSP (age 69.3 ± 10.1 years; LVEF 34.3 ± 7.7%), 133 (78.2%) patients had a narrow QRS duration, and 37 (21.2%) had an LBBB. The QRS duration changed from a baseline of 159.7 ± 16.6 ms to a paced QRS duration of 110.4 ± 12.7 ms in the LBBB cohort and from 95.6 ± 10.4 to 100.8 ± 14.5 ms (both P < 0.001) in the narrow QRS cohort after AVJ ablation and pacing. Compared with the narrow QRS cohort, the LBBB cohort showed a greater absolute increase in LVEF (+22.3% vs. +14.2%, P < 0.001), higher super responder rate (71.4% vs. 49.2%, P = 0.011), and greater New York Heart Association (NYHA) class improvement (−1.9 vs. −1.4, P < 0.001) at 1 year.

Conclusion

Patients with LBBB have greater improvement in LVEF and NYHA class function than patients with narrow QRS from HPCSP after AVJ ablation.

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.).

Cardiac resynchronization therapy setting personalization utilizing noninvasive hemodynamics

BACKGROUND

Cardiac resynchronization therapy (CRT) has been an important adjunct to goal directed medical therapy in heart failure patients who qualify for this device. Too often, when heart failure patients complain about severe fatigue, beta-blockers are immediately reduced. Personalization of settings, verified by noninvasive hemodynamics, can allow for maximizing medical therapy.

CASE

A newly diagnosed 40 year-old male presented to the heart failure clinic post hospital discharge with a severely dilated, non-ischemic cardiomyopathy. Even with an ejection fraction (EF) of 15-20%, he reports "feeling great". Increasing medications resulted in excessive fatigue. Non-invasive studies showed an average cardiac index (CI) of 1.5l/min/m². It was decided to personalize his settings. Changes made increased his CI to 3.9l/min/m².

CONCLUSION

Combining current available technology with noninvasive studies significantly improved his CI and no reduction in beta-blocker therapy was necessary. CRT personalization can be of significant value for the heart failure patient.

Design and rationale of the Impact of MultiPoint pacing in CRT patients with reduced RV-to-LV delay (IMAGE-CRT) study

BACKGROUND

Cardiac resynchronization therapy (CRT) is an established treatment in patients with heart failure and prolonged QRS duration. A biventricular device is implanted to achieve faster activation and more synchronous contraction of the ventricles. Despite the convincing effect of CRT, 30-40% of patients do not respond. We decided to investigate the role of multipoint pacing (MPP) in a selected group of patients with right ventricle (RV)-to-left ventricle (LV) intervals less than 80 ms that do not respond to traditional CRT.

METHODS

We will enrol 248 patients in this patient-blinded, observational, clinical study aiming to investigate if MPP could decrease LV end-systolic volume (ESV) in patients with RV-to-LV interval less than 80 ms. MPP will be activated ON at implant in patients with RV-to-LV delay less than 80 ms and OFF in RV-to-LV at least 80 ms. At follow-up the activation of MPP will be related to CRT response. The primary study endpoint will be the responder rate at 6 months, defined as a decrease in LV ejection fraction, LV end-diastolic volume, LV end-systolic volume (LVESV) at least 15% from baseline. Secondary outcomes include 12 months relative percentage reduction in LVESV and a combined clinical outcome measure of response to CRT defined as the patient being alive, no hospitalization due to heart failure, and experiencing an improvement in New York Heart Association functional class (Composite-Score).

CONCLUSION

Reducing the nonresponder rate continues to be an important goal for CRT.If an increase in reverse remodelling can be achieved by MPP, this study supports the conduct of larger trials investigating the role of MPP on clinical outcomes in selected patients treated, right now, only with traditional CRT.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02713308. Registered on 18 March 2016.

Optimization of Chronic Cardiac Resynchronization Therapy Using Fusion Pacing Algorithm Improves Echocardiographic Response

Background

Whether reprogramming of cardiac resynchronization therapy (CRT) to increase electrical synchrony translates into echocardiographic improvement remains unclear. SyncAV is an algorithm that allows fusion of intrinsic conduction with biventricular pacing. We aimed to assess whether reprogramming chronically implanted CRT devices with SyncAV is associated with improved echocardiographic parameters.

Methods

Patients at a quaternary center with previously implanted CRT devices with a programmable SyncAV algorithm underwent routine electrocardiography-based SyncAV optimization during regular device clinic visits. This analysis included only patients who could be programmed to the SyncAV algorithm (i.e., in sinus rhythm with intrinsic atrioventricular conduction). Echocardiography was performed before and 6 months after CRT optimization.

Results

Of 64 consecutive, potentially eligible patients who underwent assessment, 34 who were able to undergo SyncAV programming were included. Their mean age was 74 ± 9 years, 41% were female, and 59% had ischemic cardiomyopathy. The mean time from CRT implant to SyncAV optimization was 17.8 ± 8.5 months. At 6-month follow-up, SyncAV optimization was associated with a significant increase in left ventricular ejection fraction (LVEF) (mean LVEF 36.5% ± 13.3% vs 30.9% ± 13.3%; P < 0.001) and a reduction in left ventricular end-systolic volume (LVESV) (mean LVESV 110.5 ± 57.5 mL vs 89.6 ± 52.4 mL; P < 0.001) compared with baseline existing CRT programming.

Conclusion

CRT reprogramming to maximize biventricular fusion pacing significantly increased LVEF and reduced LVESV in patients with chronic CRT devices. Further studies are needed to assess if a continuous fusion pacing algorithm improves long-term clinical outcomes and to identify which patients are most likely to derive benefit.

Electrocardiographic optimization techniques in resynchronization therapy

Cardiac resynchronization therapy (CRT) is a cornerstone of therapy for patients with heart failure, reduced left ventricular (LV) ejection fraction, and a wide QRS complex. However, not all patients respond to CRT: 30% of CRT implanted patients are currently considered clinical non-responders and up to 40% do not achieve LV reverse remodelling. In order to achieve the best CRT response, appropriate patient selection, device implantation, and programming are important factors. Optimization of CRT pacing intervals may improve results, increasing the number of responders, and the magnitude of the response. Echocardiography is considered the reference method for atrioventricular and interventricular (VV) intervals optimization but it is time-consuming, complex and it has a large interobserver and intraobserver variability. Previous studies have linked QRS shortening to clinical response, echocardiographic improvement and favourable prognosis. In this review, we describe the electrocardiographic optimization methods available: 12-lead electrocardiogram; fusion-optimized intervals (FOI); intracardiac electrogram-based algorithms; and electrocardiographic imaging. Fusion-optimized intervals is an electrocardiographic method of optimizing CRT based on QRS duration that combines fusion with intrinsic conduction. The FOI method is feasible and fast, further reduces QRS duration, can be performed during implant, improves acute haemodynamic response, and achieves greater LV remodelling compared with nominal programming of CRT.

Optimization of Lead Placement in the Right Ventricle During Cardiac Resynchronization Therapy. A Simulation Study

Patients suffering from heart failure and left bundle branch block show electrical ventricular dyssynchrony causing an abnormal blood pumping. Cardiac resynchronization therapy (CRT) is recommended for these patients. Patients with positive therapy response normally present QRS shortening and an increased left ventricle (LV) ejection fraction. However, around one third do not respond favorably. Therefore, optimal location of pacing leads, timing delays between leads and/or choosing related biomarkers is crucial to achieve the best possible degree of ventricular synchrony during CRT application. In this study, computational modeling is used to predict the optimal location and delay of pacing leads to improve CRT response. We use a 3D electrophysiological computational model of the heart and torso to get insight into the changes in the activation patterns obtained when the heart is paced from different regions and for different atrioventricular and interventricular delays. The model represents a heart with left bundle branch block and heart failure, and allows a detailed and accurate analysis of the electrical changes observed simultaneously in the myocardium and in the QRS complex computed in the precordial leads. Computational simulations were performed using a modified version of the O'Hara et al. action potential model, the most recent mathematical model developed for human ventricular electrophysiology. The optimal location for the pacing leads was determined by QRS maximal reduction. Additionally, the influence of Purkinje system on CRT response was assessed and correlation analysis between several parameters of the QRS was made. Simulation results showed that the right ventricle (RV) upper septum near the outflow tract is an alternative location to the RV apical lead. Furthermore, LV endocardial pacing provided better results as compared to epicardial stimulation. Finally, the time to reach the 90% of the QRS area was a good predictor of the instant at which 90% of the ventricular tissue was activated. Thus, the time to reach the 90% of the QRS area is suggested as an additional index to assess CRT effectiveness to improve biventricular synchrony.

Optimizing Cardiac Resynchronization Therapy Devices in Follow-up to Improve Response Rates and Outcomes

Although cardiac resynchronization therapy (CRT) will improve symptoms and survival in selected heart failure patients, there still remains a high percentage of CRT recipients who do not obtain benefit from the therapy. During CRT follow-up, an effort should be made to identify and to treat reversible causes of nonresponse to CRT. This effort includes optimization of medical therapy, checking for appropriate and effective biventricular pacing, and treatment of arrhythmias and other reversible causes of CRT malfunction.

Cardiac resynchronization therapy: mechanisms of action and scope for further improvement in cardiac function

Aims

Cardiac resynchronization therapy (CRT) may exert its beneficial haemodynamic effect by improving ventricular synchrony and improving atrioventricular (AV) timing. The aim of this study was to establish the relative importance of the mechanisms through which CRT improves cardiac function and explore the potential for additional improvements with improved ventricular resynchronization.

Methods and Results

We performed simulations using the CircAdapt haemodynamic model and performed haemodynamic measurements while adjusting AV delay, at low and high heart rates, in 87 patients with CRT devices. We assessed QRS duration, presence of fusion, and haemodynamic response. The simulations suggest that intrinsic PR interval and the magnitude of reduction in ventricular activation determine the relative importance of the mechanisms of benefit. For example, if PR interval is 201 ms and LV activation time is reduced by 25 ms (typical for current CRT methods), then AV delay optimization is responsible for 69% of overall improvement. Reducing LV activation time by an additional 25 ms produced an additional 2.6 mmHg increase in blood pressure (30% of effect size observed with current CRT). In the clinical population, ventricular fusion significantly shortened QRS duration (Δ-27 ± 23 ms, P < 0.001) and improved systolic blood pressure (mean 2.5 mmHg increase). Ventricular fusion was present in 69% of patients, yet in 40% of patients with fusion, shortening AV delay (to a delay where fusion was not present) produced the optimal haemodynamic response.

Conclusions

Improving LV preloading by shortening AV delay is an important mechanism through which cardiac function is improved with CRT. There is substantial scope for further improvement if methods for delivering more efficient ventricular resynchronization can be developed.

Clinical Trial Registration

Our clinical data were obtained from a subpopulation of the British Randomised Controlled Trial of AV and VV Optimisation (BRAVO), which is a registered clinical trial with unique identifier: NCT01258829, https://clinicaltrials.gov

Programming Cardiac Resynchronization Therapy for Electrical Synchrony: Reaching Beyond Left Bundle Branch Block and Left Ventricular Activation Delay

BACKGROUND

QRS narrowing following cardiac resynchronization therapy with biventricular (BiV) or left ventricular (LV) pacing is likely affected by patient-specific conduction characteristics (PR, qLV, LV-paced propagation interval), making a universal programming strategy likely ineffective. We tested these factors using a novel, device-based algorithm (SyncAV) that automatically adjusts paced atrioventricular delay (default or programmable offset) according to intrinsic atrioventricular conduction.

METHODS AND RESULTS

Seventy-five patients undergoing cardiac resynchronization therapy (age 66±11 years; 65% male; 32% with ischemic cardiomyopathy; LV ejection fraction 28±8%; QRS duration 162±16 ms) with intact atrioventricular conduction (PR interval 194±34, range 128-300 ms), left bundle branch block, and optimized LV lead position were studied at implant. QRS duration (QRSd) reduction was compared for the following pacing configurations: nominal simultaneous BiV (Mode I: paced/sensed atrioventricular delay=140/110 ms), BiV+SyncAV with 50 ms offset (Mode II), BiV+SyncAV with offset that minimized QRSd (Mode III), or LV-only pacing+SyncAV with 50 ms offset (Mode IV). The intrinsic QRSd (162±16 ms) was reduced to 142±17 ms (-11.8%) by Mode I, 136±14 ms (-15.6%) by Mode IV, and 132±13 ms (-17.8%) by Mode II. Mode III yielded the shortest overall QRSd (123±12 ms, -23.9% [P<0.001 versus all modes]) and was the only configuration without QRSd prolongation in any patient. QRS narrowing occurred regardless of QRSd, PR, or LV-paced intervals, or underlying ischemic disease.

CONCLUSIONS

Post-implant electrical optimization in already well-selected patients with left bundle branch block and optimized LV lead position is facilitated by patient-tailored BiV pacing adjusted to intrinsic atrioventricular timing using an automatic device-based algorithm.

Advances in atrioventricular and interventricular optimization of cardiac resynchronization therapy - what's the gold standard?

INTRODUCTION

Cardiac resynchronization therapy (CRT) is one of the most important advances in heart failure management in the last twenty years. Approximately one-third of patients appear not to respond to therapy. Although there are a number of possible mechanisms for non-response, an important factor is suboptimal atrioventricular (AV) and interventricular (VV) timing intervals. There remains controversy over whether routinely optimizing intervals is necessary and there is no agreed gold standard methodology. Optimization has classically been performed using echocardiography which has limits related to resource use, time-cost and variable reproducibility. Newer optimization methods using device-based sensors and algorithms show promise in reducing heart-failure hospitalization compared with echocardiography. Areas covered: This review outlines the rationale for optimization, the principles of AV and VV optimization, the standard echocardiographic approach and newer device-based algorithms and the evidence base for their use. Expert commentary: The incremental gains of optimization are likely to be real, but small, compared to the overall improvement gained from cardiac resynchronization itself. At this time routine optimization may not be mandatory but should be performed where there is no response to CRT. Device-based optimization algorithms appear to be practical and in some cases, deliver superior clinical outcomes compared to echocardiography.

Ventricular dyssynchrony assessment using ultra-high frequency ECG technique

Purpose

The aim of this proof-of-concept study is to introduce new high-dynamic ECG technique with potential to detect temporal-spatial distribution of ventricular electrical depolarization and to assess the level of ventricular dyssynchrony.

Methods

5-kHz 12-lead ECG data was collected. The amplitude envelopes of the QRS were computed in an ultra-high frequency band of 500–1000 Hz and were averaged (UHFQRS). UHFQRS V lead maps were compiled, and numerical descriptor identifying ventricular dyssynchrony (UHFDYS) was detected.

Results

An electrical UHFQRS maps describe the ventricular dyssynchrony distribution in resolution of milliseconds and correlate with strain rate results obtained by speckle tracking echocardiography. The effect of biventricular stimulation is demonstrated by the UHFQRS morphology and by the UHFDYS descriptor in selected examples.

Conclusions

UHFQRS offers a new and simple technique for assessing electrical activation patterns in ventricular dyssynchrony with a temporal-spatial resolution that cannot be obtained by processing standard surface ECG. The main clinical potential of UHFQRS lies in the identification of differences in electrical activation among CRT candidates and detection of improvements in electrical synchrony in patients with biventricular pacing.

Electronic supplementary material

The online version of this article (doi:10.1007/s10840-017-0268-0) contains supplementary material, which is available to authorized users.

Left univentricular pacing for cardiac resynchronization therapy

This review describes the rationale and published evidence for left univentricular pacing for cardiac resynchronization therapy, gives an overview of the existing optimization algorithms featuring this mode, and discusses future perspectives.

Cardiac Resynchronization Therapy: How to Decrease Nonresponders

Nonresponse to cardiac resynchronization therapy (CRT) is still a major issue in therapy expansion. The description of fast, simple, cost-effective methods to optimize CRT could help in adapting pacing intervals to individual patients. A better understanding of the importance of appropriate patient selection, left ventricular lead placement, and device programming, together with a multidisciplinary approach and an optimal follow-up of the patients, may reduce the percentage of nonresponders.

The Role of Atrioventricular and Interventricular Optimization for Cardiac Resynchronization Therapy

Many patients with left ventricular systolic dysfunction may benefit from cardiac resynchronization therapy; however, approximately 30% of patients do not experience significant clinical improvement with this treatment. AV and VV delay optimization techniques have included echocardiography, device-based algorithms, and several other novel noninvasive techniques. Using these techniques to optimize device settings has been shown to improve hemodynamic function acutely; however, the long-term clinical benefit is limited. In most cases, an empiric AV delay with simultaneous biventricular or left ventricular pacing is adequate. The value of optimization of these intervals in "nonresponders" still requires further investigation.

Cardiac Resynchronization Therapy: How to Decrease Nonresponders

Nonresponse to cardiac resynchronization therapy (CRT) is still a major issue in therapy expansion. The description of fast, simple, cost-effective methods to optimize CRT could help in adapting pacing intervals to individual patients. A better understanding of the importance of appropriate patient selection, left ventricular lead placement, and device programming, together with a multidisciplinary approach and an optimal follow-up of the patients, may reduce the percentage of nonresponders.

Left Ventricular Lead Placement Targeted at the Latest Activated Site Guided by Electrophysiological Mapping in Coronary Sinus Branches Improves Response to Cardiac Resynchronization Therapy

INTRODUCTION

Electrophysiological mapping (EPM) in coronary sinus (CS) branches is feasible for guiding LV lead placement to the optimal, latest activated site at cardiac resynchronization therapy (CRT) procedures. However, whether this procedure optimizes the response to CRT has not been demonstrated. This study was to evaluate effects of targeting LV lead at the latest activated site guided by EPM during CRT.

METHODS

Seventy-six consecutive patients with advanced heart failure who were referred for CRT were divided into mapping (MG) and control groups (CG). In MG, the LV lead, also used as a mapping bipolar electrode, was placed at the latest activated site determined by EPM in CS branches. In CG, conventional CRT procedure was performed. Patients were followed for 6 months after CRT.

RESULTS

Baseline characteristics were comparable between the 2 groups. In MG (n = 29), EPM was successfully performed in 85 of 91 CS branches during CRT. A LV lead was successfully placed at the latest activated site guided by EPM in 27 (93.1%) patients. Compared with CG (n = 47), MG had a significantly higher rate (86.2% vs. 63.8%, P = 0.039) of response (>15% reduction in LV end-systolic volume) to CRT, a higher percentage of patients with clinical improvement of ≥2 NYHA functional classes (72.4% vs. 44.7%, P = 0.032), and a shorter QRS duration (P = 0.004).

CONCLUSIONS

LV lead placed at the latest activated site guided by EPM resulted in a significantly greater CRT response, and a shorter QRS duration.

Vectorcardiography for optimization of stimulation intervals in cardiac resynchronization therapy

Current optimization of atrioventricular (AV) and interventricular (VV) intervals in cardiac resynchronization therapy (CRT) is time consuming and subject to noise. We aimed to prove the principle that the best hemodynamic effect of CRT is achieved by cancelation of opposing electrical forces, detectable from the QRS morphology in the 3D vectorcardiogram (VCG). Different degrees of left (LV) and right ventricular (RV) pre-excitation were induced, using variation in AV intervals during LV pacing in 20 patients with left bundle branch block (LBBB) and variation in VV intervals during biventricular pacing in 18 patients with complete AV block or atrial fibrillation. The smallest QRS vector area identified stimulation intervals with minimal systolic stretch (median difference [IQR] 20 ms [−20, 20 ms] and maximal hemodynamic response (10 ms [−20, 40 ms]). Reliability of VCG measurements was superior to hemodynamic measurements. This study proves the principle that VCG analysis may allow easy and reliable optimization of stimulation intervals in CRT patients.