Potential Mechanisms Underlying the Effect of Gender on Response to Cardiac Resynchronization Therapy: Insights From the SMART-AV Multicenter Trial
Does gender influence the response to cardiac resynchronization therapy (CRT)?
This was a post-hoc analysis of 980 patients (mean age 66 years) with systolic heart failure (mean left ventricular ejection fraction [LVEF] 24%) and a bundle branch block, enrolled in a trial designed to compare atrioventricular optimization (AVO) strategies. Echocardiograms were performed at baseline and at 3 and 6 months of follow-up. The primary endpoint was change in LV end-systolic volume (LVESVi) indexed to body surface area.
Women comprised 32% of the study population. In a multivariate analysis, gender was an independent predictor of the response to CRT. The reduction in LVESVi at 6 months was significantly greater in women (13.4 ml/m2) than in men (8.5 ml/m2). Furthermore, LVEF improved to a greater degree in women than men (7.2% vs. 4.9%). The response to CRT was enhanced by AVO in women, but not men. The percent biventricular pacing at 6 months was significantly higher in women (98.8%) than in men (98.3%).
The authors concluded that women respond to a greater degree than men to CRT, at least partly because of gender-specific responses to AVO strategies.
Some prior CRT trials have reported that gender did not influence the response to CRT, whereas others have reported better outcomes in women. The present study strengthens the case for gender-related differences in the response to CRT. It seems unlikely that only a 0.5% difference in percent biventricular pacing could account for the better outcomes in women. Although the reasons are unclear, the better response to CRT in women seems attributable to an enhanced response to AVO.
Keywords: Multivariate Analysis, Follow-Up Studies, Heart Rate, Cardiac Resynchronization Therapy, Heart Diseases, Body Surface Area, Cardiac Pacing, Artificial, Heart Block, Heart Failure, Bundle-Branch Block, Stroke Volume, Ventricular Function, Atrioventricular Node, Echocardiography
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