Evaluating sex differences in population-based utilization of implantable cardioverter defibrillators: role of cardiac conditions and noncardiac comorbidities

Background — The influence of age and comorbidities on sex-specific implantable cardioverter-defibrillator (ICD) use for primary or secondary prevention is undefined.

Objective — The purpose of this study was to investigate the influence of age and comorbidities on sex-specific ICD use.

Methods — Sex disparities and sex-specific trends in ICD implantation according to indication in patients with cardiac arrest (1998–2007) in Ontario, Canada, were examined. Use of ICDs for primary prevention in patients with myocardial infarction (2002–2007) or heart failure (2005–2007) also was examined.

Results — Among 9,246 eligible secondary prevention patients (age 66.3 ± 14.3 years; 3,577 women [39%]) with cardiac arrest, men were more likely to undergo ICD implantation, with an age-, comorbidity-, and arrhythmia-adjusted hazard ratio (HR) of 1.92 (95% confidence interval [CI]: 1.66–2.23). Among 105,516 patients with myocardial infarction (age 68.3 ± 12.7 years; 42,987 women [41%]), men were threefold more likely to undergo ICD implantation, with an adjusted HR of 3.00 (95% CI: 2.53–3.55). Among 61,160 patients with heart failure (age 76.2 ± 12.0 years; 31,575 women [52%]), ICD implantation was more likely in men, with an adjusted HR of 3.01 (95% CI: 2.59–3.50). The odds of ICD implant for secondary prevention increased over time by 21% (95% CI: 13%–30%) in women and by 6% (95% CI: 2%–11%) in men, but rates of ICD use in men for primary prevention indications were persistently higher.

Conclusion — Men were more likely to undergo defibrillator implant than were women for primary and secondary prevention. Age and comorbidities did not account for the observed sex differences. Although sex differences in secondary prevention are declining over time, disparities in primary prevention persist.