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

摘要

© 2017 American College of Cardiology FoundationObjectives: 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.