Survival and arrhythmia risk in medicare patients with icd generator changes in the ncdr icd registry based on left ventricular ejection fraction at the time of generator change

Introduction: There is presently uncertainty regarding the appropriateness of performing an ICD generator change (GC) for patients with implantable cardioverter defibrillators (ICDs) and an original primary prevention indication. Hypothesis: Survival rates and arrhythmia risk in Medicare patients undergoing an ICD GC would be influenced by whether the left ventricular ejection fraction (LVEF) had improved to greater than 35% at the time of GC. Methods: Survival was evaluated in patients with Medicare coverage (age ≥ 65 years) with an original (pre-ICD) primary prevention indication undergoing an ICD GC (ORIG-PP-ICD-GC) from the NCDR ICD Registry Version 2 (excluding cardiac resynchronization therapy devices) relative to a control group without ICDs from clinical trials and registries. Data were analyzed using Kaplan-Meier survival curves and Cox proportional hazards regression. Results: Among 9,643 ORIG-PP-ICD-GC patients, 68% still had LVEF≤35%, and 32% had improved LVEF>35% at the time of GC. The frequency of antitachycardia pacing (ATP) or shock therapies prior to GC was similar in those with LVEF≤35% (20.8%) and LVEF >35% at GC (19.6%). Improved LVEF>35% at GC was associated with greater unadjusted survival (p< 0.0001; Figure), consistent with a more favorable Seattle Heart Failure Model (SHFM-D) risk score with LVEF>35% versus LVEF≤35% (-0.30 versus 0.34; p<0.0001). In a Cox proportional hazards model adjusted for SHFM-D and arrhythmia risk, ORIG-PP-ICD-GC patients as a whole had a modestly increased mortality risk versus 13,797 control patients without ICDs (HR 1.16, 95% CI 1.09-1.22, p< 0.0001). Conclusions: In this Medicare cohort with an original primary prevention ICD indication, improvement in LVEF to over 35% at GC was reported in about a third of patients and was associated with better survival overall but similar rates of ICD therapies between the initial ICD implant and GC. Overall survival after an ORIG-PP-ICD-GC was lower than expected.