Probability and magnitude of response to cardiac resynchronization therapy according to QRS duration and gender in nonischemic cardiomyopathy and LBBB

Survival in Women Versus Men Following Implantation of Pacemakers, Defibrillators, and Cardiac Resynchronization Therapy Devices in a Large, Nationwide Cohort

Background

Whether outcomes differ between sexes following treatment with pacemakers (PM), implantable cardioverter defibrillators, and cardiac resynchronization therapy (CRT) devices is unclear.

Methods and Results

Consecutive US patients with newly implanted PM, implantable cardioverter defibrillators, and CRT devices from a large remote monitoring database between 2008 and 2011 were included in this observational cohort study. Sex‐specific all‐cause survival postimplant was compared within each device type using a multivariable Cox proportional hazards model, stratified on age and adjusted for remote monitoring utilization and ZIP‐based socioeconomic variables. A total of 269 471 patients were assessed over a median 2.9 [interquartile range, 2.2, 3.6] years. Unadjusted mortality rates (MR; deaths/100 000 patient‐years) were similar between women versus men receiving PMs (n=115 076, 55% male; MR 4193 versus MR 4256, respectively; adjusted hazard ratio, 0.87; 95% CI, 0.84–0.90; P<0.001) and implantable cardioverter defibrillators (n=85 014, 74% male; MR 4417 versus MR 4479, respectively; adjusted hazard ratio, 0.98; 95% CI, 0.93–1.02; P=0.244). In contrast, survival was superior in women receiving CRT defibrillators (n=61 475, 72% male; MR 5270 versus male MR 7175; adjusted hazard ratio, 0.73; 95% CI, 0.70–0.76; P<0.001) and also CRT pacemakers (n=7906, 57% male; MR 5383 versus male MR 7625, adjusted hazard ratio, 0.69; 95% CI, 0.61–0.78; P<0.001). This relative difference increased with time. These results were unaffected by age or remote monitoring utilization.

Conclusions

Women accounted for less than 30% of high‐voltage implants and fewer than half of low‐voltage implants in a large, nation‐wide cohort. Survival for women and men receiving implantable cardioverter defibrillators and PMs was similar, but dramatically greater for women receiving both defibrillator‐ and PM‐based CRT.

Sex-Specific Response to Cardiac Resynchronization Therapy: Effect of Left Ventricular Size and QRS Duration in Left Bundle Branch Block

OBJECTIVES

In this study, the authors sought to assess the impact of body and heart size on sex-specific cardiac resynchronization therapy (CRT) response rate, according to QRS duration (QRSd) as a continuum.

BACKGROUND

Effects of CRT differ between sexes for any given QRSd.

METHODS

New York Heart Association functional class III/IV patients with nonischemic cardiomyopathy and "true" left bundle branch block (LBBB) were evaluated. Left ventricular mass (LVM) and end-diastolic volume were measured echocardiographically. Positive response was defined by left ventricular ejection fraction (LVEF) improvement post-CRT.

RESULTS

Among 130 patients (LVEF 19 ± 7.1%; QRSd 165 ± 20 ms; 55% female), CRT improved LVEF to 32 ± 14% (p < 0.001) during a median 2 years follow-up. Positive responses occurred in 103 of 130 (79%) (78% when QRSd <150 ms vs. 80% when QRSd ≥150 ms; p = 0.8). Body surface area (BSA), QRSd, and LVM were lower in women, but QRSd/LVM ratio greater (p < 0.0001). Sexes did not differ for pharmacotherapy and comorbidities, but female CRT response was greater: 90% (65 of 72) versus 66% (38 of 58) in males (p < 0.001). With QRSd as a continuum, the overall CRT-response relationship showed a progressive increase to plateau between 150 and 170 ms, then a decrease. Sex-specific differences were conspicuous: among females, a peak effect was observed between 135 and 150 ms, thereafter a decline, with the male response rate lower, but with a gradual increase as QRSd lengthened. Sex-specific differences were unaltered by BSA, but resolved with integration of LVM or end-diastolic volume.

CONCLUSIONS

Sex differences in the QRSd-response relationship among CRT patients with LBBB were unexplained by application of strict LBBB criteria or by BSA, but resolved by QRSd normalization for heart size using LV mass or volume.

Effect of Gender on Outcomes After Cardiac Resynchronization Therapy in Patients With a Narrow QRS Complex

Background—

In EchoCRT, a randomized controlled trial evaluating the effect of cardiac resynchronization therapy (CRT) in patients with a QRS duration of <130 ms and echocardiographic evidence of left ventricular dyssynchrony, the primary outcome (death from any cause or first hospitalization for worsening heart failure) occurred more frequently in the CRT-ON when compared with the control group. In this prespecified subgroup analysis, we evaluated the effect of sex on clinical outcome in EchoCRT.

Methods and Results—

In EchoCRT, 585 (72%) of included patients were men. At baseline, male patients had a higher incidence of ischemic cardiomyopathy and longer QRS duration. On uni- and multivariable analysis, no significant interaction was observed regarding sex for the primary or any of the secondary end points. Numerically, a higher all-cause mortality was observed in male patients randomized to CRT-ON versus CRT-OFF on univariable analysis (hazard ratio, 1.83; 95% confidence interval, 1.08–3.12); however, no statistically significant interaction compared with females randomized to CRT-ON versus CRT-OFF was noted (hazard ratio, 0.99; P interaction, 0.56). There was no difference in the primary safety end point of system-related complications, including CRT system- and implantation-related events.

Conclusions—

The largest hazard for all-cause mortality in EchoCRT was observed in men randomized to CRT-ON; the comparison with women did not reach statistical significance, which may be because of the premature termination of the trial and the limited data. These results suggest that male sex may be a risk factor for harm by CRT in patients with narrow QRS width, an observation which deserves further investigation.

Clinical Trial Registration—

URL: https://clinicaltrials.gov . Unique identifier: NCT00683696.

Early Changes in QRS Frequency Following Cardiac Resynchronization Predict Hemodynamic Response in Left Bundle Branch Block Patients

INTRODUCTION

QRS characteristics are the cornerstone of patient selection in cardiac resynchronization therapy (CRT) and the presence of left bundle branch block (LBBB) and baseline QRS ≥150 milliseconds portends a good outcome. We previously showed that baseline QRS frequency analysis adds predictive value to LBBB alone and have hypothesized that a change in frequency characteristics following CRT may produce additional predictive value.

METHODS

We examined the QRS frequency characteristics of 182 LBBB patients before and soon after CRT. Patients were assigned to responder and nonresponder groups. Responders were defined by a decrease in left ventricular end-systolic volume (LVESV) ≥15% following CRT. We analyzed the QRS in ECG leads I, AVF, and V3 before and soon after CRT using the discrete Fourier transform algorithm. The percentage of total QRS power within discrete frequency intervals before and after CRT was calculated. The reduction in lead V3 power <10 Hz was the best indicator of response.

RESULTS

Baseline QRS width was similar between the responders and nonresponders (162.2 ± 17.2 milliseconds vs. 158 ± 22.1 milliseconds, respectively; P = 0.180). Responders exhibited a greater reduction in QRS power <10 Hz (-17.0 ± 11.9% vs. -6.6 ± 12.5%; P < 0.001) and a significant AUC (0.743; P < 0.001). A ≥8% decline in QRS power <10 Hz produced the best predictive values (PPV = 84%, NPV = 59%). Importantly, when patients with baseline QRS <150 milliseconds were compared, the AUC improved (0.892, P < 0.001).

CONCLUSIONS

Successful CRT produces a significant reduction in QRS power below 10 Hz, particularly when baseline QRS <150 milliseconds. These results indicate that QRS frequency changes after CRT provide additional predictive value to QRS alone.

Adjusting the QRS Duration by Body Mass Index for Prediction of Response to Cardiac Resynchronization Therapy: Does One QRS Size Fit All?

BACKGROUND

QRS duration (QRSd) is known to be affected by body weight and length. We tested the hypothesis that adjusting the QRSd by body mass index (BMI) may provide individualization for patient selection and improve prediction of cardiac resynchronization therapy (CRT) response.

METHODS

A total of 125 CRT recipients was analyzed to assess functional (≥1 grade reduction in NYHA class) and echocardiographic (≥15% reduction in LVESV) response to CRT at 6 months of implantation. Baseline QRSd was adjusted by BMI to create a QRS index (QRSd/BMI) and tested for prediction of CRT response in comparison to QRSd.

RESULTS

Overall, 81 patients (65%) responded to CRT volumetrically. The mean QRS index was higher in CRT responders compared to nonresponders (6.2 ± 1.1 vs 5.2 ± 0.8 ms.m(2) /kg, P < 0.001). There was a positive linear correlation between the QRS index and the change in LVESV (r = 0.487, P < 0.001). Patients with a high QRS index (≥5.5 ms.m(2) /kg, derived from the ROC analysis, AUC = 0.787) compared to those with a prolonged QRSd (≥150 ms, AUC = 0.729) had a greater functional (72% vs 28%, P < 0.001) and echocardiographic (80% vs 44%, P < 0.001) improvement at 6 months. QRS index predicted CRT response at regression analysis.

CONCLUSIONS

Indexing the QRSd by BMI improves patient selection for CRT by eliminating the influence of body weight and length on QRSd. QRS index is a novel indicator that provides promising results for prediction of CRT response.

Cardiac Resynchronization Therapy in Women

The benefits of cardiac resynchronization therapy (CRT) on the outcomes of patients with heart failure are unquestionable. Women are under-represented in all CRT studies. Most of the available data show that CRT produces a greater clinical benefit in women than men. In several studies, women have left bundle branch block more frequently than men. Women have a remarkably high (90%) CRT response over a wide range of QRS lengths (130-175 milliseconds). Use of a QRS duration of 150 milliseconds as the threshold for CRT prescription may deny a life-saving therapy to many women likely to benefit from CRT.

Sex Differences in Utilisation and Response to Implantable Device Therapy

Multiple studies have demonstrated that implantable cardioverter-defibrillators (ICDs) and cardiac resynchronisation therapy (CRT) provide significant mortality and morbidity benefits to eligible patients irrespective of gender. However, female patients are less likely to receive this life-saving therapy and are significantly under-represented in cardiac device trials. Various performance improvement programmes have proved that this gender disparity can be reduced and these therapies should be offered to all eligible patients regardless of sex. Efforts should be made to enrol more women in clinical trials and sex-specific analysis in medical device clinical studies should be encouraged. In this article we review the data on sex differences in clinical outcomes with ICDs and CRT and explore the reasons for this sex-based disparity.

Sex Differences in Long-Term Outcomes With Cardiac Resynchronization Therapy in Mild Heart Failure Patients With Left Bundle Branch Block

Background

Previous studies have shown conflicting results regarding the benefit of cardiac resynchronization therapy (CRT) by sex and QRS duration.

Methods and Results

In the Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy (MADIT-CRT), we evaluated long-term clinical outcome of heart failure (HF) or death, death, and HF alone by sex and QRS duration (dichotomized at 150 ms) in left bundle-branch block patients with CRT with defibrillator backup (CRT-D) versus implantable cardioverter-defibrillator (ICD) only. There were 394 women (31%) and 887 men with left bundle-branch block. During the median follow-up of 5.6 years, women derived greater clinical benefit from CRT-D compared with implantable cardioverter-defibrillator only, with a significant 71% reduction in HF or death (hazard ratio [HR] 0.29, P<0.001) and a 77% reduction in HF alone (HR 0.23, P<0.001) compared with men, who had a 41% reduction in HF or death (HR 0.59, P<0.001) and a 50% reduction in HF alone (HR 0.50, P<0.001) (all sex-by-treatment interaction P<0.05). Men and women had similar reduction in long-term mortality with CRT-D versus implantable cardioverter-defibrillator only (men: HR 0.70, P=0.03; women: HR 0.59, P=0.04). The incremental benefit of CRT-D in women for HF or death and HF alone was consistent with QRS <150 or >150 ms.

Conclusions

During long-term follow-up of mild HF patients with left ventricular dysfunction and wide QRS, both women and men with left bundle-branch block derived sustained benefit from CRT-D versus implantable cardioverter-defibrillator only, with significant reduction in HF or death, HF alone, and all-cause mortality regardless of QRS duration. There is an incremental benefit with CRT-D in women for the end points of HF or death and HF alone.

Clinical Trial Registration

URL: https://clinicaltrials.gov/. Unique identifiers: NCT00180271, NCT01294449, and NCT02060110.

Noninvasive mapping of electrical dyssynchrony in heart failure and cardiac resynchronization therapy

Causes for diverse effects of cardiac resynchronization therapy (CRT) are poorly understood. Because CRT is an electrical therapy, it may be best understood by detailed characterization of electrical substrate and its interaction with pacing. Electrocardiogram (ECG) features affect CRT outcomes. However, the surface ECG reports rudimentary electrical data. In contrast, noninvasive electrocardiographic imaging provides high-resolution single-beat ventricular mapping. Several complex characteristics of electrical substrate, not decipherable from the 12-lead ECG, are linked to CRT effect. CRT response may be improved by candidate selection and left ventricular lead placement directed by more precise electrical evaluation, on an individual patient basis.