WASHINGTON, July 1, 2010 — New large meta-analysis from five primary prevention randomized implantable cardioverter-defibrillator (ICD) studies shows a smaller impact of Sudden Cardiac Death (SCD) on overall mortality in women. According to research published in the July edition of the HeartRhythm Journal, the official journal of the Heart Rhythm Society, women in primary prevention ICD trials have the same overall mortality as men, while experiencing significantly less appropriate ICD interventions. With more than 1,600 women, this meta-analysis includes the largest cohort of women to date.
The study was designed to evaluate primary prevention ICD trials that assessed gender differences with the end points of total mortality, appropriate ICD interventions and survival benefits compared to placebo. The meta-analysis study included 7,229 patients, 22 percent women, with dilated cardiomyopathy enrolled in five different studies: MADIT-II, MUSTT, SCD-HeFT, DEFINITE and COMPANION. To ensure direct comparisons between women and men, analysis for each study was adjusted for the maximum number of confounding factors and covariates in order to provide approximations that would be affected the least by standard gender differences.
Overall study findings revealed women had the same overall mortality as men (hazard ratio 0.96, p = 0.84). However, women experienced significantly less ICD interventions on rapid sustained ventricular tachycardia or fibrillation than men (hazard ratio 0.63, p ≤ 0.001), suggesting that women are less likely to suffer from SCD. Additionally, among men ICD therapy was associated with a 33 percent reduction of total mortality compared to the placebo group while women had a smaller and nonsignificant reduction of mortality.
"Our main focus was to compare women to men when it came to clinical outcomes following prophylactic ICD placement to determine if certain subgroups of patients should be treated differently," said lead author Pasquale Santangeli of the Cardiology Department at Catholic University in Rome, Italy. "We believe that our findings may explain why women have a smaller and nonsignificant survival benefits from prophylactic ICD therapy and the importance for further studies to be done on this underrepresented subgroup – women."
Many studies previously conducted have underrepresented women in primary prevention ICD trials, and this study demonstrates that women do benefit differently from ICD therapies than men. Therefore, the study suggests that women should be considered more often in trials to continue discoveries for the best outcomes and preventative measures for each gender.