Left ventricular paced activation in cardiac resynchronization therapy patients with left bundle branch block and relationship to its electrical substrate

Acute Hemodynamic Effect of a Novel Dual-Vein, Multisite Biventricular Pacing Configuration

BACKGROUND

Biventricular pacing (BVP) from multiple left ventricular (LV) sites could enhance the efficacy of cardiac resynchronization therapy (CRT) by engaging a greater myocardial mass.

OBJECTIVES

The goal of this study was to evaluate the acute hemodynamic effect of various multisite pacing (MSP) configurations against conventional BVP.

METHODS

Twenty patients with nonischemic dilated cardiomyopathy and left bundle branch block (mean age: 59 ± 14 years; LV ejection fraction: 27% ± 6%; native QRS: 171 ± 16 milliseconds) were investigated during a routine CRT implant procedure. In addition to conventional right atrial and right ventricular leads, 2 quadripolar leads were placed in the distant coronary venous branches. LV hemodynamics was evaluated by using a micromanometer-tipped catheter during atrioventricular BVP with 4 LV lead configurations: single-lead conventional BVP; single-lead multipoint pacing; triventricular pacing from distal dipoles of 2 LV leads; and maximum MSP (MSP-Max) from 4 dipoles of 2 LV leads.

RESULTS

Compared with right atrial pacing, any BVP configuration produced a significant increase in the maximal LV diastolic pressure rise (LVdP/dTMax) (a median relative increase of 28% [IQR: 8%-45%], 25% [IQR: 18%-46%], 36% [IQR: 18%-54%], and 38% [IQR: 28%-58%], respectively; all, P < 0.001). MSP-Max but no other multisite BVP generated a significant increase of the maximal LVdP/dTMax than conventional BVP (P = 0.041). Increased LVdP/dTMax during MSP-Max was associated with greater LV diameter and lower LV ejection fraction, independently of the QRS width.

CONCLUSIONS

The study shows the hemodynamic advantage of a novel dual-vein MSP-Max configuration that could be useful for CRT in patients with advanced LV remodeling.

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.

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.

Vectorcardiographic QRS area as a predictor of response to cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is a good treatment for heart failure accompanied by ventricular conduction abnormalities. Current ECG criteria in international guidelines seem to be suboptimal to select heart failure patients for CRT. The criteria QRS duration and left bundle branch block (LBBB) QRS morphology insufficiently detect left ventricular activation delay, which is required for benefit from CRT. Additionally, there are various definitions for LBBB, in which each one has a different association with CRT benefit and is prone to subjective interpretation. Recent studies have shown that the objectively measured vectorcardiographic QRS area identifies left ventricular activation delay with higher accuracy than any of the current ECG criteria. Indeed, various studies have consistently shown that a high QRS area prior to CRT predicts both echocardiographic and clinical improvement after CRT. The beneficial relation of QRS area with CRT-outcome was largely independent from QRS morphology, QRS duration, and patient characteristics known to affect CRT-outcome including ischemic etiology and sex. On top of QRS area prior to CRT, the reduction in QRS area after CRT further improves benefit. QRS area is easily obtainable from a standard 12-lead ECG though it currently requires off-line analysis. Clinical applicability will be significantly improved when QRS area is automatically determined by ECG equipment.

Intracardiac conduction time as a predictor of cardiac resynchronization therapy response: Results of the BIO|SELECT pilot study

Background

Quadripolar left ventricular (LV) leads are capable of sensing and pacing the left ventricle from 4 different electrodes, which may potentially improve patient response to cardiac resynchronization therapy (CRT).

Objective

We measured 3 different time intervals: right ventricular (RV)-sensed to LV-sensed during intrinsic rhythm (RVs-LVs), RV-paced to LV-sensed (RVp-LVs), and LV-paced to LV-sensed (LVp-LVs, between distal [LV1] and proximal pole on a quadripolar LV lead), and assessed their association with CRT response in terms of LV end-systolic volume (LVESV) and a composite benefit index (CBI) comprising LVESV, LV ejection fraction (LVEF), brain natriuretic peptide level, and NYHA class.

Methods

A CRT-defibrillator system with quadripolar LV lead was implanted in 196 patients (mean age 69 years, mean LVEF 30%, left bundle-branch block [LBBB] 58%). Conduction intervals were measured before hospital discharge. At baseline and 7-month follow-up, echocardiographic and other components of CBI were determined.

Results

The mean RVs-LV1s, RVp-LV1s, and LVp-LVs delays were 68 ± 38 ms, 132 ± 34 ms, and 99 ± 31 ms, respectively. From baseline to 7 months, LVESV decreased by 17.3% ± 28.6%. The RVs-LV1s interval correlated stronger with CBI (R² = 0.12, P < .00001) than with LVESV change (R² = 0.05, P = .006). In contrast, RVp-LV1s did not correlate and LVp-LVs correlated only weakly with CRT response. The subgroup of patients (44%) with LBBB and RVs-LV1s above the lower quartile (≥34 ms) showed the greatest response to CRT.

Conclusion

The RVs-LVs interval during intrinsic rhythm is relevant for CRT success, whereas RVp-LVs and LVp-LVs intervals did not predict CRT response.

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.

Ventricular activation patterns during intrinsic conduction and right ventricular pacing in cardiac resynchronization therapy patients

BACKGROUND

Cardiac resynchronization therapy (CRT) involves stimulation of both right ventricle (RV) and left ventricle (LV). LV pacing from the sites of delayed electrical activation improves CRT response. The RV-LV conduction is typically measured in intrinsic rhythm. The differences in RV-LV conduction patterns and timing between intrinsic rhythm and during paced RV activation, these differences are not fully understood.

METHODS

Enrolled patients were implanted with a de novo CRT device and quadripolar LV lead, with lead implant locations at the implanting physician's discretion. QRS duration and conduction delay between the RV lead and each of the four LV electrodes (D1, M2, M3, and P4) were measured during intrinsic conduction and RV pacing.

RESULTS

Conduction measurements were collected from 275 patients across 14 international centers (68 ± 13 years of age, 73% male, 45% ischemic, 158 ± 22 ms QRS duration). Mean RV-LV conduction time was shorter during intrinsic conduction versus RV pacing by 59.6 ms (106.5 ± 36.5 versus 166.1 ± 32.1 ms, p < 0.001). The intra-LV activation delay between the latest and earliest activating LV electrode was also shorter during intrinsic conduction versus RV pacing by 6.6 ms (20.6 ± 13.1 vs. 27.2 ± 21.2 ms, p < 0.001). Intrinsic conduction and RV pacing resulted in a different activation order in 72.7% of patients, and the same LV activation order in 27.3%.

CONCLUSIONS

Differences in RV-LV conduction time, intra-LV conduction time, and activation pattern were observed between intrinsic conduction and RV pacing. These findings highlight the importance of evaluating intrinsic versus paced ventricular activation to guide LV pacing site selection in CRT patients.

Gain in real-world cardiac resynchronization therapy efficacy with SyncAV dynamic optimization: Heart failure hospitalizations and costs

BACKGROUND

SyncAV, a device-based cardiac resynchronization therapy (CRT) algorithm, promotes electrical optimization by dynamically adjusting atrioventricular intervals.

OBJECTIVE

The purpose of this study was to evaluate the impact of SyncAV on heart failure hospitalizations (HFHs) and related costs in a real-world CRT cohort.

METHODS

Patients with SyncAV-capable CRT devices followed by remote monitoring and enrolled in Medicare fee-for-service for at least 1 year preimplant and up to 2 years postimplant were studied. Patients with SyncAV OFF were 4:1 matched to those with SyncAV ON on preimplant HFH rate, demographics, comorbidities, disease etiology, and left bundle branch block. HFHs were determined from the primary diagnosis of inpatient hospitalizations, and the cost for each event was the sum of Medicare, supplemental insurance, and patient payment.

RESULTS

After 4:1 propensity score matching, 3630 patients were studied (mean age 75 ± 8 years; 1386 [38%] female), including 726 (25%) patients with SyncAV ON. The pre-CRT HFH rate was 0.338 HFH events per patient-year. Overall, CRT diminished the HFH rate to 0.204 events per patient-year (P < .001). SyncAV elicited a larger reduction in HFH rate (SyncAV ON: hazard ratio [HR] 0.52; 95% confidence interval [CI] 0.41-0.66; P < .001 and SyncAV OFF: HR 0.68; 95% CI 0.59-0.77; P < .001). After 2 years, the HFH rate was lower in the SyncAV ON group than in the SyncAV OFF group (0.143 HFHs per patient-year vs 0.193 HFHs per patient-year; HR 0.70; 95% CI 0.55-0.89; P = .003) and fewer HFHs were followed by 30-day HFH readmissions (4.41% vs 7.68%; P = .003) and 30-day all-cause hospital readmissions (7.04% vs 10.01%; P = .010). The total 2-year HFH-associated costs per patient were lower with SyncAV ON (difference $1135; 90% CI $93-$2109; P = .038).

CONCLUSION

This large, real-world, propensity score-matched study demonstrates that SyncAV CRT is associated with significantly reduced HFHs and associated costs, incremental to standard CRT.

Reduction in the QRS area after cardiac resynchronization therapy is associated with survival and echocardiographic response

INTRODUCTION

Recent studies have shown that the baseline QRS area is associated with the clinical response after cardiac resynchronization therapy (CRT). In this study, we investigated the association of QRS area reduction (∆QRS area) after CRT with the outcome. We hypothesize that a larger ∆QRS area is associated with a better survival and echocardiographic response.

METHODS AND RESULTS

Electrocardiograms (ECG) obtained before and 2-12 months after CRT from 1299 patients in a multi-center CRT-registry were analyzed. The QRS area was calculated from vectorcardiograms that were synthesized from 12-lead ECGs. The primary endpoint was a combination of all-cause mortality, heart transplantation, and left ventricular (LV) assist device implantation. The secondary endpoint was the echocardiographic response, defined as LV end-systolic volume reduction ≥ of 15%. Patients with ∆QRS area above the optimal cut-off value (62 µVs) had a lower risk of reaching the primary endpoint (hazard ratio: 0.43; confidence interval [CI] 0.33-0.56, p < .001), and a higher chance of echocardiographic response (odds ratio [OR] 3.3;CI 2.4-4.6, p < .0001). In multivariable analysis, ∆QRS area was independently associated with both endpoints. In patients with baseline QRS area ≥109 µVs, survival, and echocardiographic response were better when the ∆QRS area was ≥62 µVs (p < .0001). Logistic regression showed that in patients with baseline QRS area ≥109 µVs, ∆QRS area was the only significant predictor of survival (OR: 0.981; CI: 0.967-0.994, p = .006).

CONCLUSION

∆QRS area is an independent determinant of CRT response, especially in patients with a large baseline QRS area. Failure to achieve a large QRS area reduction with CRT is associated with a poor clinical outcome.

Optimizing lead placement for pacing in dyssynchronous heart failure: The patient in the lead

Cardiac resynchronization therapy (CRT) greatly reduces morbidity and mortality in patients with dyssynchronous heart failure. However, despite tremendous efforts, response has been variable and can be further improved. Although optimizing left ventricular lead placement (LVLP) is arguably the cornerstone of CRT, the procedure of LVLP using the transvenous approach has remained largely unchanged for more than 2 decades. Improvements have been developed using scar location and electrical and/or mechanical mapping, and interest in conduction system pacing as an alternative to biventricular pacing has emerged recently. Conduction system pacing is promising but may not be suitable for all patients with dyssynchronous heart failure. This review underscores the importance of a patient-tailored approach and discusses the potential applications of both conduction system pacing and targeted biventricular CRT.

Left Ventricular Enlargement, Cardiac Resynchronization Therapy Efficacy, and Impact of MultiPoint Pacing

Background:

Left ventricular (LV) epicardial pacing results in slowly propagating paced wavefronts. We postulated that this effect might limit cardiac resynchronization therapy efficacy in patients with LV enlargement using conventional biventricular pacing with single-site LV pacing, but be mitigated by LV stimulation from 2 widely spaced sites using MultiPoint pacing with wide anatomic separation (MPP-AS: ≥30 mm). We tested this hypothesis in the multicenter randomized MPP investigational device exemption trial.

Methods:

Following implant, quadripolar biventricular single-site pacing was activated in all patients (n=506). From 3 to 9 months postimplant, among patients with available baseline LV end-diastolic volume (LVEDV) measures, 188 received biventricular single-site pacing and 43 received MPP-AS. Patients were dichotomized by median baseline LVEDV indexed to height (LVEDVI Median ). Outcomes were measured by the clinical composite score (primary efficacy end point), quality of life, LV structural remodeling (↑EF >5% and ↓ESV 10%) and heart failure event/cardiovascular death.

Results:

LVEDVI Median was 1.1 mL/cm. Baseline characteristics differed in patients with LVEDVI >Median versus LVEDVI ≤Median . Among patients with LVEDVI >Median , biventricular single-site pacing was less efficacious compared to patients with LVEDVI ≤Median (clinical composite score, 65% versus 79%). In contrast, MPP-AS programming generated greater clinical composite score response (92% versus 65%, P =0.023) and improved quality of life (−31.0±29.7 versus −15.7±22.1, P =0.038) versus biventricular single-site pacing in patients with LVEDVI >Median . Reverse remodeling trended better with MPP-AS programming. In patients with LVEDVI >Median , heart failure event rate increased following the 3-month randomization point with biventricular single-site pacing (0.0150±0.1725 in LVEDVI >Median versus −0.0190±0.0808 in LVEDVI ≤Median , P =0.012), but no heart failure event occurred in patients with MPP-AS programming between 3 and 9 months in LVEDVI >Median . All measured outcomes did not differ in patients receiving MPP-AS and biventricular single-site pacing with LVEDVI ≤Median .

Conclusions:

Conventional biventricular single-site pacing, even with a quadripolar lead, has reduced efficacy in patients with LV enlargement. However, the greatest response rate in patients with larger hearts was observed when programmed to MPP-AS pacing.