ATLANTA — Women may not derive a significant mortality benefit from implantable cardioverter defibrillator therapy, Nickole N. Henyan, Pharm.D., said at the annual meeting of the American College of Cardiology.
She presented a metaanalysis examining the effect of gender on all-cause mortality in the major randomized, controlled trials of implantable cardioverter defibrillator (ICD) therapy for primary prevention of arrhythmic death.
The metaanalysis included five randomized trials totalling 6,405 subjects, 1,575 of them women. The risk of all-cause mortality in men who received an ICD was reduced by 26% relative to controls who got the then-standard therapy. In contrast, the relative risk reduction in women with an ICD was 19%, which didn't attain statistical significance, said Dr. Henyan of the University of Connecticut School of Pharmacy, Storrs, and Hartford (Conn.) Hospital.
When the metaanalysis was redone after excluding the 1,520-patient Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial, on the grounds that it studied ICD therapy in combination with biventricular pacing, the gender disparity in all-cause mortality became even more pronounced. Men who got an ICD showed a highly significant 24% reduction in all-cause mortality compared with male controls, whereas women who received an ICD had only a nonsignificant 12% relative risk reduction.
“Perhaps we're overtreating women by implanting ICDs for primary prevention,” Dr. Henyan said. “There are concerns of cosmetic alteration and inappropriate shocks that come with an ICD, and no patient should have to endure this unless significant life-saving benefit results.”
Session moderator Dr. Douglas P. Zipes was skeptical. “Those data are extremely provocative. To my knowledge, ventricular fibrillation is the same whether you're a man or a woman, and a shock should terminate it. I have no answer as to why there should be a gender difference to an ICD response, assuming patients are matched in terms of sickness and ejection fraction,” said Dr. Zipes, distinguished emeritus professor of medicine at Indiana University, Indianapolis.
Dr. Henyan noted that any metaanalysis should be viewed as hypothesis-generating rather than as the final word. She said one possible explanation for the observed gender difference is that it could be an artifact resulting from the limited number of women included in the analysis.
