Sex Differences in the Use of Implantable Cardioverter-Defibrillators for Primary and Secondary Prevention of Sudden Cardiac Death

Abstract

Previous studies of sex differences in the use of implantable cardioverter-defibrillators (ICDs) predate recent expansions in Medicare coverage and did not provide patient follow-up over multiple years. To examine sex differences in ICD use for primary and secondary prevention of sudden cardiac death. Analysis of a 5% national sample of research-identifiable files obtained from the US Centers for Medicare & Medicaid Services for the period 1991 through 2005. Patients were those aged 65 years or older with Medicare fee-for-service coverage and diagnosed with acute myocardial infarction and either heart failure or cardiomyopathy but no prior cardiac arrest or ventricular tachycardia (ie, the primary prevention cohort [n = 65,917 men and 70,504 women]), or with cardiac arrest or ventricular tachycardia (ie, the secondary prevention cohort [n = 52,252 men and 47,411 women]), from 1999 through 2005. Receipt of ICD therapy and all-cause mortality at 1 year. In the 2005 primary prevention cohort, 32.3 per 1000 men and 8.6 per 1000 women received ICD therapy within 1 year of cohort entry. In multivariate analyses, men were more likely than women to receive ICD therapy (hazard ratio [HR], 3.15; 95% confidence interval [CI], 2.86-3.47). Among men and women alive at 180 days after cohort entry, the hazard of mortality in the subsequent year was not significantly lower among those who received ICD therapy (HR, 1.01; 95% CI, 0.82-1.23). In the 2005 secondary prevention cohort, 102.2 per 1000 men and 38.4 per 1000 women received ICD therapy. Controlling for demographic variables and comorbid conditions, men were more likely than women to receive ICD therapy (HR, 2.44; 95% CI, 2.30-2.59). Among men and women alive at 30 days after cohort entry, the hazard of mortality in the subsequent year was significantly lower among those who received ICD therapy (HR, 0.65; 95% CI, 0.60-0.71). In the Medicare population, women are significantly less likely than men to receive ICD therapy for primary or secondary prevention of sudden cardiac death.