[Risk of mortality after myocardial infarction: value of heart rate, its variability and left ventricular ejection...

Heart rate variability is a useful parameter for risk stratification after myocardial infarction. However, the relationship between heart rate itself and its variability has not been adequately studied. The authors compared the average RR interval of 24 hours recorded by Holter monitoring with the variability of heart rate and of left ventricular ejection fraction to assess the risk of death after myocardial infarction. A total of 579 patients was followed up for 2 years after acute myocardial infarction. During this period, there were 54 deaths, 42 of cardiac origin, 26 being classified as sudden death. The positive predictive value of left ventricular ejection fraction was lower than those of mean RR interval and the variability of heart rate for overall mortality, cardiac mortality and sudden death. The three indices were essentially equivalent for the prediction of non-sudden cardiac death. The positive predictive value of heart rate variability was better than the mean RR interval for sensitivities < 40%, for all cause mortality. However, for sensitivities > 40%, the two parameters were equivalent or slightly in favour of the mean heart rate over 24 hours. The authors conclude that the mean RR interval over 24 hours is an important prognostic index after myocardial infarction. This index is more powerful than left ventricular ejection fraction and comparable to heart rate variability.