Benefit of Implantable Cardioverter-Defibrillator Generator Replacement in a Primary Prevention Population-Based Cohort

Objectives This study investigated the benefit of an implantable cardioverter-defibrillator (ICD) generator replacement in patients who did not have an ongoing theoretical indication for ICD therapy at time of replacement. Background Primary prevention ICD therapy is known to reduce mortality in patients with cardiomyopathy and reduced left ventricular systolic function. The data describing outcomes after generator replacement are limited. Methods This was a retrospective cohort study following patients implanted with primary prevention ICD therapy from 2002 until 2015 who subsequently received a generator replacement. Patients with an ongoing theoretical indication for ICD therapy were defined as either left ventricular ejection fraction ≤35% or having had prior appropriate ICD therapy. Outcomes were mortality, appropriate ICD therapy and shock, inappropriate shock, and device and lead complications. Results A total of 614 patients were identified; 173 (28.2%) underwent a generator replacement and were followed for a mean of 2.9 years after replacement; 144 (83.2%) had an ongoing theoretical indication. Patients with no ongoing theoretical indication (n = 29, 16.7%) had lower mortality (hazard ratio [HR]: 0.39, 95% confidence interval [CI]: 0.15-1.00; p = 0.0495), appropriate shock rate (HR: 0.29, 95% CI: 0.09 to 0.96; p = 0.04), and appropriate ICD therapy rate (HR: 0.30, 95% CI: 0.12 to 0.77; p = 0.012) when compared with patients with ongoing theoretical indication. In the entire cohort, there were low rates of inappropriate shock (4.0%), device complication (5.1%), and lead complication (2.3%). Conclusions In patients with primary prevention ICD therapy who underwent generator replacement, improved left ventricular ejection fraction and lack of prior appropriate ICD therapy at time of replacement were associated with a lower risk of mortality and incident ventricular arrhythmia.