POPULATION-BASED OUTCOMES OF ICD THERAPY IN WOMEN

Abstract

Although randomized controlled trials have established the survival benefit of implantable cardioverter-defibrillators (ICDs) in the prevention of sudden cardiac death, controversy remains as to whether this benefit applies equally to women and men. Due to the low enrolment of women in the ICD trials, population-based data examining sex differences in ICD outcomes may provide further clarification. Study data were derived from a provincial registry in British Columbia (BC) - the Cardiac Services BC Registry. All recipients of an ICD in BC are recorded in the Registry. Patients ≥18 years with a new ICD implant from Jan 2003 to Dec 2012 were included and linked with data from BC Vital Statistics to determine all-cause mortality. Survival was assessed using Kaplan-Meier (KM) methods stratified by sex and compared using the log-rank test. The Cox proportional-hazards model was used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) between sexes. The effects of baseline characteristics (demographics, comorbidities and medication use) were explored and only factors with a p-value < 0.15 were included in the final adjusted model. Statistical analyses were performed using SAS software, version 9.3 (Cary, NC). During the study period, 3905 new ICD implants were performed. Of these, 704 (18%) were women. Women in the cohort, compared to men, were younger (59.6 vs. 63.5 years), respectively, and had a lower prevalence of comorbid conditions (Table). Except for beta-blocker use, women were less likely to be prescribed cardiac medications such as ACE inhibitors and anti-arrhythmics. The KM survival estimates were 0.95 at 1-year for both sexes, 0.79 for women and 0.73 for men at 5 years, and 0.70 for women and 0.57 for men at 8 years; the overall survival of women was greater than men (Figure). After adjusting for age, diabetes, coronary artery disease, congestive cardiomyopathy, peripheral vascular disease, acquired heart surgery, and anti-arrhythmic drug use, in the Cox proportional-hazards model, the sex difference in mortality was attenuated and no longer significant, adjusted HR 0.91, (95% CI: 0.75,1.12). Mortality trends from our population reveal that there is no difference in survival between women and men with ICDs. This may imply that women with ICDs derive the same benefit as men. Ongoing analyses will determine whether the impact of sex on mortality is different among patients receiving an ICD for primary versus secondary prevention and among those with ICDs compared to a similar population without ICDs.View Large Image Figure ViewerDownload (PPT)