Risk prediction in post-infarction patients with moderately reduced left ventricular ejection fraction by combined assessment of the sympathetic and vagal cardiac autonomic nervous system

Abstract

AimMost deaths after myocardial infarction (MI) occur in patients with normal or moderately reduced left ventricular ejection fraction (LVEF >35%). Periodic repolarization dynamics (PRD) and deceleration capacity (DC) are novel ECG-based markers related to sympathetic and vagal cardiac autonomic nervous system activity. Here, we test the combination of PRD and DC to predict risk in post-infarction patients with LVEF >35%. Methods and resultsWe included 823 survivors of acute MI with LVEF >35%, aged ≤80years and in sinus rhythm. PRD and DC were obtained from 30-min ECG-recordings within the second week after index infarction and dichotomized at established cut-off values of ≥5.75deg2 and ≤2.5ms, respectively. Patients were classified as having normal (CAF 0), partly abnormal (DC or PRD abnormal; CAF 1) or abnormal cardiac autonomic function (DC and PRD abnormal; CAF 2). Primary endpoint was 5-year all-cause mortality. Within the first 5years of follow-up, 51 patients died (6.2%). PRD and DC effectively stratified patients into low-risk (CAF 0; n=562), intermediate-risk (CAF 1; n=193) and high-risk patients (CAF 2; n=68) with cumulative 5-year mortality rates of 2.9%, 9.4% and 25.2%, respectively (p<0.001). On multivariable analyses, CAF was independent from established risk factors (GRACE-score, diabetes mellitus, mean heart rate, heart rate variability). Addition of CAF significantly improved the model (increase of C-statistics from 0.732 (0.651–0.812) to 0.777 (0.703–0.850), p=0.047; continuous NRI (0.400, 95% CI 0.230–0.560, p<0.001); IDI (0.056, 95% CI 0.022–0.122, p<0.001)). ConclusionCAF identifies new high-risk post-MI patients with LVEF >35% which might benefit from prophylactic strategies.