Background Heart Rate Score (HrSc), a novel index found to predict mortality in patients with implantable defibrillator (ICD) and cardiac resynchronization defibrillator (CRT-D) devices, is associated with mortality in ICD and CRT-D recipients when HrSc is >= 70%. Implantable defibrillator shocks have also been associated with increased mortality in ICD and CRT-D recipients. The objective of this study was to evaluate the relationships between HrSc, shocks, and mortality in ICD and CRT-D patients. Methods HrSc was calculated from atrial sensed and paced rate histograms collected from the 2006-2011 ALTITUDE remote interrogation database. Shocks were determined in the first year of follow-up. Mortality was assessed over the next 4 years by the Social Security Death Index. Four multivariable models were run: ICD and CRT-D, shock and no shock, with mortality as the outcome and HrS as predictor. Results Data from 49,358 ICD and 55,953 CRT-D patients were divided into HrSc: >= 70%, 30-69%, and 70%; p = 70% to HrSc = 70% predicted mortality in CRT-D (HR 1.40; 95% CI 1.29-1.52) and ICD (HR 1.23; 95% CI 1.11-1.36) patients regardless of shocks (P < 0.001 for both). Conclusions Patients with ICDs or CRT-Ds having the lowest mortality risk HrSc had the highest shock rate. Shocks and HrSc appear to complement each other as predictors of mortality.
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