Does the Benefit of Secondary Prevention Implantable Cardioverter-Defibrillators Vary Based on the Estimated Proportional Risk of Sudden Death?

Introduction: The Seattle Proportional Risk Model (SPRM) is a validated model developed in systolic heart failure patients without implantable cardioverter-defibrillators (ICDs) to estimate the proportion of all-cause mortality (ACM) due to sudden death. This study aims to ascertain if SPRM has utility in risk stratification for secondary prevention ICD. Methods: The AVID (Antiarrhythmics Versus Implantable Defibrillators) trial was a multicenter, randomized clinical trial in which 1,016 patients presenting with ventricular fibrillation or sustained, symptomatic ventricular tachycardia were randomized to ICD or antiarrhythmic (AA) drug therapy. Using routine clinical variables, we applied the SPRM to patient-level data (n=995 with complete data) and assessed if the ICD benefit for ACM varied with SPRM-predicted probability of sudden death. Results: SPRM was predictive of sudden death vs. non-sudden death in patients without an ICD (logistic regression p=0.005). The ICD hazard ratio for ACM was 0.59. ICD survival benefit varied with SPRM for ACM (p=0.013) with benefit (ICD HR≤0.80) seen in patients with SPRM>40%. ICD benefit trended higher in patients with a history of heart failure (HF) vs no HF (HR=0.52 vs. 0.81, interaction p=0.13) (Figure 1). In comparison to the AA group, patients with either HF or SPRM>51% (median) had a meaningful ICD benefit (HR=0.60, p=0.017), and patients with both HF and SPRM>51% had the greatest ICD benefit (HR=0.38, p<0.001). There was no ICD benefit if no HF and SPRM<51% (HR=1.17). Conclusions: In a population of patients with VF or sustained VT, secondary prevention ICDs decreased ACM by 41%. ICD survival benefit varied with SPRM-predicted proportion of sudden death, and trended higher in patients with HF. SPRM may therefore provide a useful tool for risk stratifying patients for secondary prevention ICD. Figure 1: Survival benefit for ICD therapy varies with SPRM-estimated proportion of sudden death, and HF versus no HF.