THE EFFECT OF CARDIAC RESYNCHRONIZATION THERAPY ON OUTCOMES IN WOMEN: A SUBSTUDY OF THE RESYNCHRONIZATON FOR AMBULATORY HEART FAILURE TRIAL

Abstract

Cardiac resynchronization therapy defibrillator (CRT-D) has demonstrated reduced mortality and heart failure hospitalizations in patients with left ventricular dysfunction and left bundle branch block (LBBB). Prior studies have demonstrated that women may benefit more than men from CRT-D. We sought to further evaluate this hypothesis in a post hoc analysis of the Resynchronization for Ambulatory Heart Failure Trial (RAFT) on mortality and heart failure hospitalization. The RAFT study has the advantage of longer duration of follow up than any of the other studies on CRT-D. Data collection was performed as part of the RAFT study which included 1798 patients with a QRS >120ms or paced >200ms and LVEF < 30%. Baseline characteristics were compared to determine differences between men and women. In a multivariable Cox proportional hazards model, outcomes (mortality and heart failure hospitalization) were compared between men and women. There were 1490 (83%) men (732 ICD, 758 CRT-D) and 308 (17%) women (172 ICD, 136 CRT-D) included in the analysis. Mean follow up in the study was 40 months. Women had more non-ischemic heart disease (54.87% vs 28.72%, p= < 0.0001) and LBBB (89.61% vs 82.28%, p=0.0016) as well as worse NYHA Class (III) (25.32% vs 18.93%, p=0.0106), but less ischemic heart disease (45.13% vs 71.28%, p= < 0.0001), permanent atrial fibrillation (9.09% vs 13.49%, p=0.035), previous PCI/CABG (29.55% vs 52.89%, p= < 0.0001), and peripheral vascular disease (6.82% vs 10.54%, p=0.0467). Differences in QRS duration were not significant. Women with CRT-D had significantly reduced incidence of death and heart failure hospitalization after adjusting for baseline differences compared to men with CRT-D (See Table; referent category is women with CRT-D). These differences persisted after adjustment for age, type of heart disease, NYHA Class, permanent AF/AFl, previous PCI/CABG, smoking, peripheral vascular disease, EGFR, LBBB or IVCD, baseline medications and QRS duration. Women have a more favourable outcome with CRT-D as compared to men, even after adjusting for differences in baseline characteristics over a prolonged follow up. Whether these improved outcomes are due to inherent differences in the underlying myocardial substrate between men and women or whether they are due to an enhanced response to CRT-D will require further study.