Gender, underutilization of cardiac resynchronization therapy, and prognostic impact of QRS prolongation and left bundle branch block in heart failure

AIMS: It has been suggested that cardiac resynchronization therapy (CRT) is less utilized, dyssynchrony occurs at narrower QRS, and CRT is more beneficial in women compared with men. We tested the hypotheses that (i) CRT is more underutilized and (ii) QRS prolongation and left bundle branch block (LBBB) are more harmful in women. METHODS AND RESULTS: We studied 14 713 patients (28% women) with left ventricular ejection fraction (LVEF) <40% in the Swedish Heart Failure Registry. In women vs. men, CRT was present in 4 vs. 7% (P < 0.001) and was absent but with indication in 30 vs. 31% (P = 0.826). Next, among 13 782 patients (28% women) without CRT, 9% of women and 17% of men had non-specific intraventricular conduction delay (IVCD) and 27% of women and 24% of men had LBBB. One-year survival with narrow QRS was 85% in women and 88% in men, with IVCD 74 and 78%, and with LBBB 84 and 82%, respectively. Compared with narrow QRS, IVCD had a multivariable hazard ratio of 1.24 (95% CI 1.05-1.46, P = 0.011) in women and 1.30 (95% CI 1.19-1.42, P < 0.001) in men, and LBBB 1.03 (95% CI 0.91-1.16, P = 0.651) in women and 1.16 (95% CI 1.07-1.26, P < 0.001) in men, P for interaction between gender and QRS morphology, 0.241. CONCLUSIONS: While the proportion with CRT was lower in women, CRT was equally underutilized in both genders. QRS prolongation with or without LBBB was not more harmful in women than in men. Efforts to improve CRT implementation should be directed equally towards women and men.