Abstract 2435: Heart Rate Predicts Outcomes in an Implantable Defibrillator Population
Introduction: Elevated resting heart rate (HR) is associated with adverse cardiovascular events and total mortality in the general population and in individuals with heart disease.
Hypothesis: Mean HR predicts total mortality and heart failure hospitalization in patients with heart disease undergoing ICD implantation.
Methods: The Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) Study enrolled 1,530 patients who had a standard ICD indication for primary or secondary prevention. Its primary endpoint was a composite of total mortality and heart failure hospitalization. After implantation of a dual chamber ICD, patients were followed for a mean of 10.4 months. Data regarding mean heart rate (HR), obtained from device histograms, were available from 1,436 patients over the entire follow-up. Patients were grouped into strata by mean HR and the relationship between the primary endpoint and mean HR was analyzed using Mantel-Haentzel ordinal chi-square tests.
Results: Higher intrinsic (non-paced) HR was associated with greater risk of death or heart failure hospitalization (p<0.001). During the duration of the study, 7% of patients with a mean HR <65 vs. 21% with a mean HR >90 died or were hospitalized for heart failure, a 3-fold difference in events (p<0.0001, table⇓).
Conclusion: In this ICD population, long-term mean intrinsic HR was strongly associated with outcomes. More analysis is needed to understand the relationships between intrinsic HR, mortality and heart failure hospitalization.