Sex differences in ICD benefit

Implantable cardioverter defibrillators (ICD) have been demonstrated to improve survival, but a considerable number of patients never receive appropriate therapy. The influence of sex on ICD effectiveness in primary prophylactic ICD therapy is unclear.

Until now, guideline recommendations are equal for men and women, yet only an average of 20% of enrolled patients in large randomized ICD studies were women. Epidemiological data from the Framingham Heart Study exhibit lower incidences of SCD in women (≈50%). This difference is in only in part owed to less severe underlying cardiac disease or comorbidities but it persists after correction of confounding factors. Several of the large randomized studies have conducted gender substudies. In MADIT-II, the survival benefit for women was similar as for men, although the risk of appropriate ICD therapy was lower for women. In SCD-HeFT and DEFINITE, the survival benefits for women were less compared to men, or not existent. Trends were contradictingly summarized by two meta-analyses. By this important post-hoc research, important hypotheses for prospective work in the ICD subgroup of women are generated. At the same time, it is undisputed that the complication rate of ICD implantations is higher in women. The largest ICD registry to date Ontario (Canada) confirms the lower appropriate shock rate in women but found no differences in total mortality.

Further subgroup analyses of large ICD cohorts by sex are needed, as well as studies investigating the influence of sex on ICD treatment--and potentially ICD indication--prospectively.