Sex difference in appropriate shocks but not mortality during long-term follow-up in patients with implantable cardioverter-defibrillators

Aims: Implantable cardioverter-defibrillators (ICDs) have been shown to improve survival, although a considerable number of patients never receive therapy. Implantable cardioverter-defibrillators are routinely implanted regardless of sex. There is continuing controversy whether major outcomes differ between men and women.

Methods and results: In this retrospective single-centre study, 1151 consecutive patients (19% women) undergoing ICD implantation between 1998 and 2010 were followed for mortality and first appropriate ICD shock over 4.9 ± 2.7 years. Sex-related differences were investigated using multivariable Cox models adjusting for potential confounders. During follow-up, 318 patients died, a rate of 5.9% per year among men and 4.6% among women (uncorrected P = 0.08); 266 patients received a first appropriate ICD shock (6.3% per year among men vs. 3.6% among women, P = 0.002). After multivariate correction, independent predictors of all-cause mortality were age (hazard ratio, HR = 1.04 per year of age, 95% confidence interval (CI) [1.03-1.06], P < 0.001), left ventricular ejection fraction (HR = 0.98 per %, 95% CI [0.97-1.00], P = 0.025), renal function (HR = 0.99 per mL/min/1.73 m(2), 95% CI [0.99-1.00], P = 0.009), use of diuretics (HR = 1.81, 95% CI [1.29-2.54], P = 0.0023), peripheral arterial disease (HR = 2.21, 95% CI [1.62-3.00], P < 0.001), and chronic obstructive pulmonary disease (HR = 1.48, 95% CI [1.13-1.94], P = 0.029), but not sex. Female sex (HR = 0.51, 95% CI [0.33-0.81], P = 0.013), older age (HR = 0.98, 95% CI [0.97-0.99], P < 0.001), and primary prophylactic ICD indication (HR = 0.69, 95% CI [0.52-0.93], P = 0.043) were independent predictors for less appropriate shocks.

Conclusion: Women receive 50% less appropriate shocks than men having similar mortality in this large single-centre population. These data may pertain to individually improved selection of defibrillator candidates using risk factors, e.g. sex as demonstrated in this study.