Sex differences in left ventricular electrical dyssynchrony and outcomes with cardiac resynchronization therapy

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sex-based differences in cardiac resynchronization therapy upgrade and outcome for patients with pacemaker and new-onset heart failure

BACKGROUND

Patients with chronic right ventricular (RV) pacing are at an increased risk of heart failure. Previous studies have indicated that cardiac resynchronization therapy (CRT) is underused in this setting, and that there may be sex-based differences in both CRT use and clinical outcome.

OBJECTIVE

To evaluate sex-based differences in CRT use and clinical outcome for patients with new-onset heart failure post RV pacing.

METHODS

Data from the Swedish pacemaker registry was matched with data from the national death and disease registries. Patients with de novo pacemaker implant due to AV block during the period 2005-2020 were included. New-onset heart-failure within two years post-implant was evaluated, primary outcome was all-cause mortality.

RESULTS

In all, 30183 patients (37% female) were included. Women were on average 3 years older, but had less comorbidities than men. Median follow-up time was 4.5 [2.0-8.0] years. Women had better age- and comorbidity-adjusted survival (HR 0.78 [0.73-0.84], p < .001). For the 3560 patients (12.4% men and 10.7% women, p < .001) who were diagnosed with new-onset heart failure, 5-year mortality was similar for men and women (50% vs. 48%, p = .29). However, women were less likely to receive CRT-upgrade (3.8% vs. 9.1%, p < .001), and those who did were almost ten years younger than the men.

CONCLUSION

Women with pacemaker due to AV block are older but have less comorbidities than men. They are less likely to develop new-onset heart failure, but also less likely to receive a CRT upgrade if they do develop heart failure. Increased awareness of the positive effects of CRT upgrade and potential sex- and age-based discrimination is warranted.

Biventricular or Conduction System Pacing for Cardiac Resynchronization Therapy: A Strategy for Cardiac Resynchronization Based on a Hybrid Approach

BACKGROUND

Cardiac resynchronization therapy (CRT) is usually performed with biventricular pacing (BiVP), but recently, conduction system pacing (CSP) has been proposed as an alternative in case of BiVP failure. The aim of this study is to define an algorithm to choose between BiVP and CSP resynchronization using the interventricular conduction delays (IVCD) as a guide.

METHODS

Consecutive patients from January 2018 to December 2020 with an indication for CRT were prospectively enrolled in the study group (delays-guided resynchronization group, DRG). A treatment algorithm based on IVCD was used to decide whether to leave the left ventricular (LV) lead to perform BiVP or pull it out and perform CSP. Outcomes from the DRG group were compared to a historical cohort of CRT patients who underwent CRT procedures between January 2016 and December 2017 (resynchronization standard guide group, SRG). The primary endpoint was a composite of cardiovascular mortality, heart failure (HF) hospitalization, or HF event at 1 year after the date of intervention.

RESULTS

The study population consisted of 292 patients, of which 160 (54.8%) were in the DRG and 132 (45.2%) in the SRG. In the DRG, 41 of 160 patients underwent CSP based on the treatment algorithm (25.6%). The primary endpoint was significantly higher in the SRG (48/132, 36.4%) compared to the DRG (35/160, 21.8%) (hazard ratio (HR): 1.72; 95% confidence interval (CI): 1.12-2.65; p = 0.013).

CONCLUSIONS

A treatment algorithm based on IVCD shifted one patient out of every four from BiVP to CSP, with consequent reduction in the primary endpoint after implantation. Therefore, its application could be useful to determine whether to perform BiVP or CSP.

Women are underrepresented in cardiac resynchronization therapy trials

INTRODUCTION

Current guidelines for cardiac resynchronization therapy (CRT) device implant are the same across both sexes however women have been traditionally underrepresented in randomized controlled trials (RCTs). We aimed to identify if the number of women included in CRT trials is representative of the real-world burden of heart failure (HF) in women.

METHODS

RCTs evaluating the benefit of CRT in HF patients referenced in the 2012 EHRA/HRS expert consensus statement on CRT in HF were included. Studies were evaluated for gender representation, baseline variables, and gender-based analysis of outcomes.

RESULTS

A total of 10 CRT trials including 8107 patients were studied. Of the total patient population in these RCTs, only 23% were women. Analysis of outcomes based on sex was reported only in 5 out of 10 trials. Of these five trials reporting sex-based outcomes, multicenter automatic defibrillator implantation trial with cardiac resynchronization therapy (MADIT-CRT) and resynchronization-defibrillation for ambulatory heart failure trial (RAFT) showed a greater benefit in women compared to men. Both MADIT and RAFT trials had a lower ejection fraction (EF) cut-off in the inclusion criteria (EF ≤ 30%) compared to the studies that did not find gender-based differences in the outcome (inclusion criteria: EF ≤ 35% or 40%). Additionally, women had less ischemic cardiomyopathy and more left bundle branch block (LBBB) compared to men in these two trials.

CONCLUSION

Women are underrepresented in CRT trials; however, they have been shown to derive a greater benefit from CRT compared to men. Appropriate measures should be taken in future studies to enhance the participation of women in clinical trials for more generalizable evidence.