Heart rate variability in myocardial infarction with and without malignant arrhythmias: comparison with heart transplant recipients and normal subjects.

Myocardial autonomic denervation occurs after acute MI. This process is followed by a reduction of heart rate variability (HRV) and an increase of malignant ventricular arrhythmias and sudden death. This study investigated whether there are any significant differences in HRV among the population of MI who did and did not have malignant ventricular arrhythmias (MVAs), normal subjects and heart transplant recipients, the paradigm of the denervated heart. We studied 25 subjects aged 42 +/- 17 years, with normal clinical and cardiac noninvasive evaluation (group A); 70 patients aged 57 +/- 14 years, who had MI but no arrhythmic event in 36 months of follow-up (group B); 13 patients with MI aged 65 +/- 9 years, who had had sustained VT, VF, or sudden death (group C); and 16 cardiac transplant recipients aged 35 +/- 14 years (group D). The ECG was sampled for 256 seconds. We calculated, in time and frequency domain, the standard deviation of the RR cycle length and the spectral component's very low frequency (< 0.05 Hz), low frequency (0.05-0.15 Hz), and high frequency (0.15-0.35 Hz). The values of HRV in group A were significantly greater than in groups B, C, and D (P < 0.001) and greater in group B than in groups C and D (P < 0.001). Groups C and D did not differ (P = 0.610). These data indicate that HRV of patients who have had an MI and MVAs is very similar to that of heart transplant recipients. This is an indirect evidence that myocardial autonomic denervation may play an important role in the genesis of malignant arrhythmic events.