Long-term adaptation of 24-h heart rate variability after myocardial infarction. The EAMI Study Group. Exercise Training in Anterior Myocardial Infarction.

Abstract

To investigate the effects of physical training on neurovegetative profile of patients with previous anterior myocardial infarction (MI), we studied 38 patients out of the EAMI study at 4 to 6 weeks after anterior MI (test 1), who were then assigned randomly to a training group (n = 22) or to a control group (n = 16) and studied again 6 months later (test 2). Neurovegetative function was assessed by analyzing the heart rate variability (HRV) of 24 h, from ambulatory ECG recording, both in time domain, as standard deviation of sinus rhythm RR intervals (sdRR) and percentage of differences greater than 50 ms for successive sinus rhythm R-R intervals (pNN50), and in frequency domain, as low frequency (LF) and high frequency (HF) components of RR variability power spectrum. At test 1, HRV was almost in normal range or slightly decreased in few subjects. HRV increased on average at test 2: sdRR augmented significantly (p less than 0.05) without significant differences between training group and control group; mean LF/HF ratio increased slightly (p less than 0.05) at test 2. This might suggest a shift of neurovegetative balance toward a sympathetic rule, but the difference is too small and the patient population limited to reach firm conclusions. Analysis of 24-h dynamics of HRV in single patients showed different patterns and different adaptations during the time course of 6 months after anterior MI.