Heart Rate Recovery

Abstract

How quickly the heart rate recovers after treadmill exercise testing has been the subject of much interest over the last several years. The observations of Imai et al1 first prompted the clinical evaluation of heart rate recovery. In healthy subjects, athletes, and patients with heart failure, they demonstrated that early (within 1 minute) heart rate recovery was principally the result of vagal reactivation. The phenomenon was abolished by atropine, unaffected by β-blockers, independent of workload or age, blunted with heart failure, and accelerated in athletes. The hypothesis joining heart rate recovery and mortality arose from work that associated the autonomic nervous system with sudden cardiac death in the postinfarction setting.2 This hypothesis has developed to the point at which autonomic tone is considered a cardiovascular risk factor.3 Particular interest has focused on the ability of heart rate recovery to predict all-cause mortality.4–13 See p 2851 Michael Lauer’s group from The Cleveland Clinic has been the driving force behind this field of investigation. In this issue of Circulation , these investigators present a further, provocative analysis of data from their center that explores the question of whether heart rate recovery can predict who will survive after coronary revascularization. In their study, Chen et al14 address an issue that is typically dealt with via randomized controlled studies. In lieu of such a trial, they compiled observational data and applied a modified case-control study design. From a group of 8861 patients who underwent treadmill exercise tests with imaging, they found 552 patients who underwent early (ie, within 3 months of the exercise study) coronary revascularization. Using propensity matching, Chen and colleagues were able to match 508 patients from this group with 508 patients from the >8000 patients who did not undergo early revascularization. The final study group of …