Use of primary prevention implantable cardioverter-defibrillators in a population-based cohort is associated with a significant survival benefit

Background-Underuse of implantable defibrillators has been previously noted in patients at risk for sudden cardiac death, as well as for survivors of sudden cardiac death. We sought to determine the utilization rates in a primary prevention implantable cardioverter-defibrillator (ICD)-eligible population and mortality in this group compared with a group that had undergone implantation of this therapy. Methods and Results-A retrospective cohort of patients from April 1, 2006, to December 31, 2009, was used to define a primary prevention ICD-eligible population. Two groups were compared on the basis of ICD implantation (no-ICD versus ICD). The primary outcome measure was mortality. Of the 717 patients found to be potentially eligible for a primary prevention ICD, 116 (16%) were referred. The remaining cohort of 601 patients were compared with an existing cohort of primary prevention ICD patients (n=290). A significant survival benefit was associated with primary prevention ICD implantation (hazard ratio, 0.46; 95% CI [0.33-0.64]; P<0.0001). When adjusted for prespecified variables known to be associated with overall mortality and propensity score, a similar survival benefit was seen (hazard ratio, 0.59; 95% CI [0.40-0.87]; P=0.01). Appropriate ICD therapy occurred in 26% of those in the ICD group, during a mean follow-up of 2.7 years. Conclusions-A significant mortality benefit was observed for patients who underwent primary prevention ICD implantation compared with those who did not. Vigilance is required to ensure that patients eligible for primary prevention ICDs are appropriately referred and assessed to allow such patients to benefit from this life-saving therapy.