Heart-rate turbulence after ventricular premature beats as a predictor of mortality after acute myocardial infarction

Background Identification of high-risk patients after acute myocardial infa rction is essential for successful prophylactic therapy. The predictive acc uracy of currently used risk predictors is modest even when several factors are combined. Thus, establishment of a new powerful method for risk predic tion independent of the available stratifiers is of considerable practical value, Methods The study investigated fluctuations of sinus-rhythm cycle length af ter a single ventricular premature beat recorded in Holter electrocardiogra ms, and characterised the fluctuations (termed heart-rate turbulence) by tw o numerical parameters, termed turbulence onset and slope. The method was d eveloped on a population of 100 patients with coronary heart disease and bl indly applied to the population of the Multicentre Post-Infarction Program (MPIP; 577 survivors of acute infarction, 75 deaths during a median follow- up of 22 months) and to the placebo population of the European Myocardial A miodarone Trial (EMIAT; 614 survivors of acute myocardial infarction, 87 de aths during median follow-up of 21 months). Multivariate risk stratificatio n was done with the new parameters and conventional risk factors. Findings One of the new parameters (turbulence slope) was the most powerful stratifier of follow-up mortality in EMIAT and the second most powerful st ratifier in MPIP: MPIP risk ratio 3.5 (95% CI 2.2-5.5, p<0.0001), EMIAT ris k ratio 2.7 1.8-4.2, p<0.0001), In the multivariate analysis, low left-vent ricular ejection fraction and turbulence slope were the only independent va riables for mortality prediction in MPIP (p<0.001), whereas in EMIAT, five variables were independent mortality predictors: abnormal turbulence onset, abnormal turbulence slope, history of previous infarction, low left-ventri cular ejection fraction, and high mean heart rate (p<0.001). In both MPIP a nd EMIAT, the combination of abnormal onset and slope was the most powerful multivariate risk stratifier: MPIP risk ratio 3.2 (1.7-6.0, p<0.0001), EMI AT risk ratio 3.2 (1.8-5.6, p<0.0001). Interpretation The absence of the heart rate turbulence after ventricular p remature beats is a very potent postinfarction risk stratifier that is inde pendent of other known risk factors and which is stronger than other presen tly available risk predictors.