Reproducibility of time- and frequency-domain indices of heart rate variability assessed after acute myocardial infarction

The most frequent clinical use of heart rate variability (HRV) is the identification of those survivors of acute myocardial infarction who are at risk of serious ventricular arrhythmias and/or sudden cardiac death. This study assessed day-to-day reproducibility of the whole spectrum of HRV parameters in survivors of acute phase of myocardial infarction. A 48 hour ambulatory ECG recording was performed in 21 patients on day 5-7 after hospital admission. The study revealed: (a) that under clinically stable conditions the reproducibility of different time-domain and frequency domain indices of HRV is high, and (b) that day-to-day differences in HRV assessment have presumably no effect on its predictive value. At the same time, individual subjects may exhibit marked day-to-day variation of HRV measures, especially those strongly related to the vagal tone. This should be considered when assessing natural course of the disease or the effects of therapeutic interventions