Key result
Female sex was associated with better long-term outcomes after cardiac resynchronization therapy (HR 0.623), but this survival advantage was no longer significant after accounting for differences in QRS area.
Why the study?
Women derive more benefit from cardiac resynchronization therapy than men, but the electrophysiological basis for this sex difference is unclear.
Cohort (n=492)
No
Hazard Ratio: 0.623 (95% CI 0.454–0.857)
p-value: p=0.004
Background Women seem to derive more benefit from cardiac resynchronization therapy (CRT) than men, even after accounting for the higher burden of risk factors for nonresponse often observed in men. Objective To assess for sex-specific differences in left ventricular (LV) electrical dyssynchrony as a contributing electrophysiological explanation for the greater degree of CRT benefit among women. Methods We compared the extent of baseline LV electrical dyssynchrony, as measured by the QRS area (QRSA), among men and women with left bundle branch block (LBBB) undergoing CRT at Duke University (n = 492, 35% women) overall and in relation to baseline QRS characteristics using independent sample t tests and Pearson correlation coefficients. Cox regression analyses were used to relate sex, QRSA, and QRS characteristics to the risk of cardiac transplantation, LV assist device implant, or death. Results Although the mean QRS duration (QRSd) did not differ by sex, QRSA was greater for women vs men (113.8 μVs vs 98.2 μVs, P < .001), owing to differences in the QRSd <150 ms subgroup (92.3 ± 28.7 μVs vs 67.6 ± 26.2 μVs, P < .001). Among those with nonstrict LBBB, mean QRSd was similar but QRSA was significantly greater among women than men (96.0 ± 25.0 μVs vs 63.6 ± 26.2 μVs, P < .001). QRSA was similar among men and women with strict LBBB ( P = .533). Female sex was associated with better long-term outcomes in an unadjusted model (hazard ratio 0.623, confidence interval 0.454–0.857, P = .004) but sex no longer predicted outcomes after accounting for differences in QRSA. Conclusions Our study suggests that sex-specific differences in LV dyssynchrony contribute to greater CRT benefit among women. Standard QRSd and morphology assessments seem to underestimate the extent of LV electrical dyssynchrony among women with LBBB.
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Friedman et al. (2020) conducted a cohort in Heart failure with left bundle branch block undergoing cardiac resynchronization therapy (n=492). Female sex vs. Male sex was evaluated on Composite of incident LVAD, cardiac transplant, or death (HR 0.623, 95% CI 0.454-0.857, p=0.004). Female sex was associated with better long-term outcomes after cardiac resynchronization therapy (HR 0.623), but this survival advantage was no longer significant after accounting for differences in QRS area.
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