Abstract 2499: Women Have Smaller Benefit From Primary Prevention Defibrillator Therapy: A Meta-Analysis
Background. Women are underrepresented in primary prevention implantable cardioverter-defibrillator (ICD) trials and data on the benefit of ICD therapy in this subgroup are controversial. To better evaluate the benefit of prophylactic ICD therapy in women we performed a meta-analysis of primary prevention ICD trials that assessed gender differences on the end-points of total mortality, appropriate ICD therapy and survival benefit of ICD compared to placebo.
Methods. Pubmed, CENTRAL and other databases were searched (May 2009). Trials were included in the meta-analysis only if they separately examined gender differences in the specified end-points, providing the hazard ratio (HR) obtained in multiple Cox regression analyses, with the highest level of adjustment for confounding variables and covariates from each study, in order to adjust for the baseline clinical characteristics. A random effect inverse variance weighted meta-analysis was performed, by entering directly the logarithm of the hazard ratio (HR). Data are expressed as Hazard Ratio (HR) with 95% confidence interval (CI). Two tailed p value <0.05 was considered statistically significant.
Results. We retrieved 5 studies (MADIT-II, MUSTT, SCD-HeFT, DEFINITE, COMPANION) that enrolled 6905 patients with dilated cardiomyopathy (72% ischemic), of whom 1628 (24%) were women. During a mean follow-up of 41±18 months, 1608 (23%) deaths occurred. No significant difference in overall mortality was observed in women compared with men (HR 0.90 [95% CI 0.64 to 1.25], p=0.52). On the other hand, women experienced significantly less appropriate ICD interventions (HR 0.71 [95% CI 0.53 to 0.95], p=0.02). As a result, the benefit of ICD on mortality was significantly higher in men (HR 0.67 [95% CI 0.58 to 0.78], p<0.001), whereas in women did not reach statistical significance (HR 0.78 [95% CI 0.57 to 1.05], p=0.1).
Conclusions. Women enrolled in primary prevention ICD trials have the same mortality compared to men, while experiencing significantly less appropriate ICD interventions, thus suggesting a lower impact of sudden cardiac death on overall mortality in women with dilated cardiomyopathy. These findings may explain the smaller ICD survival benefit among women.