Background and aim: In the Improved Stratification of Autonomic Regulation-Risk trial, postinfarction patients with severe autonomic failure (SAF)-defined as abnormal heart rate turbulence in the presence of abnormal deceleration capacity (DC)-were at high risk of subsequent death, even if left ventricular function was not particularly compromised. The aim of this study was to investigate SAF as a risk predictor in independent postinfarction cohorts.
Methods and results: The data of 3 postinfarction trials (ie, St George's Hospital Medical School Postinfarction Survey, Holter substudy of the European Myocardial Infarction Amiodarone Trial with both the placebo and the amiodarone arms, and Multiple Risk Factor Analysis Trial) were reanalyzed in a blinded fashion. The populations included a total of 2534 postinfarction patients. Heart rate turbulence and DC were obtained from 24-hour Holter recordings. Patients with both abnormal heart rate turbulence (slope < or =2.5 ms/R-R and onset > or =0%) and abnormal DC (< or =4.5 milliseconds) were considered suffering from SAF and prospectively classified as high risk. Primary end point was all-cause mortality. During follow-up, 291 of 2534 patients died. In all populations, SAF was a highly significant predictor of death in the subgroups of patients with preserved left ventricular ejection fraction (LVEF; >30%). The mortality risk of these patients was not statistically different from that of patients with impaired LVEF (< or =30%). The combined use of the criteria, LVEF of 30% or less and LVEF of more than 30% as well as SAF lead to a significant increase of sensitivity in all populations, whereas the positive predictive accuracies were preserved.
Conclusion: In postinfarction patients with preserved left ventricular function, SAF identifies a subgroup with increased mortality risk equivalent to patients with LVEF of 30% or less.