Heart Rate Turbulence as a Predictor of Cardiac Mortality and Arrhythmic Events in Patients with Dilated Cardiomyopathy: A Prospective Study

Abstract

Few studies have described the clinical usefulness of heart rate turbulence (HRT), an autonomic predictor of mortality, in stratifying patients with dilated cardiomyopathy (DCM) at risk of cardiac mortality and arrhythmic events. We prospectively assessed the utility of HRT for risk stratification in patients with ischemic or nonischemic DCM. We enrolled 375 consecutive patients with DCM including ischemic (n = 241) and nonischemic causes (n = 134). HRT was measured using an algorithm based on routine 24-hour Holter electrocardiograms, assessing 2 parameters: turbulence onset (TO) and turbulence slope (TS). HRT was considered positive when both TO was > or = 0% and TS was < or = 2.5 ms/R-R interval. The primary endpoint was defined as cardiac mortality and the secondary endpoint as occurrence of hemodynamically stable sustained ventricular tachyarrhythmias. Of patients enrolled, 83 patients (22.1%) were not utilized for HRT assessment because there were too few ventricular premature beats, or for other reasons. Eighty-one of 292 patients (27.7%) were HRT-positive. During follow-up of 445 +/- 216 days, 30 patients (10.3%) reached the primary endpoint and 17 patients, the secondary endpoint. The hazard ratio (HR) of patients with an HRT-positive outcome was 6.4 (95%CI, 3.0-14.1; P < 0.0001) for the primary endpoint and 5.1 (95%CI, 2.8-9.3; P < 0.0001) for combined endpoints. On subanalysis, HRT positivity was significantly associated in both the ischemic and nonischemic DCM patients with both the primary endpoint (HR = 4.9, P = 0.0006 and HR = 12.3, P = 0.002, respectively) and with combined endpoints. HRT is a powerful risk stratification marker for cardiac mortality and arrhythmic events in patients with DCM whether ischemia is present or not.