Improved Stratification of Autonomic Regulation for risk prediction in post-infarction patients with preserved left ventricular function (ISAR-Risk)

To investigate the combination of heart rate turbulence (HRT) and deceleration capacity (DC) as risk predictors in post-infarction patients with left ventricular ejection fraction (LVEF) > 30%. We enrolled 2343 consecutive survivors of acute myocardial infarction (MI) (< 76 years) in sinus rhythm. HRT and DC were obtained from 24 h Holter recordings. Patients with both abnormal HRT (slope <= 2.5 ms/RR and onset >= 0%) and abnormal DC (<= 4.5 ms) were considered suffering from severe autonomic failure (SAF) and prospectively classified as high risk. Primary and secondary endpoints were all-cause, cardiac, and sudden cardiac mortality within the first 5 years of follow-up. During follow-up, 181 patients died; 39 deaths occurred in 120 patients with LVEF <= 30%, and 142 in 2223 patients with LVEF > 30% (cumulative 5-year mortality rates of 37.9% and 7.8%, respectively). Among patients with LVEF > 30%, SAF identified another high-risk group of 117 patients with 37 deaths (cumulative 5-year mortality rates of 38.6% and 6.1%, respectively). Merging both high-risk groups (i.e. LVEF <= 30% and/or SAF) doubled the sensitivity of mortality prediction compared with LVEF <= 30% alone (21.1% vs. 42.1%, P < 0.001) while preserving 5-year mortality rate (38.2%). In post-MI patients with LVEF > 30%, SAF identifies a high-risk group equivalent in size and mortality risk to patients with LVEF <= 30%.