Baroreflex sensitivity determined by spectral method and heart rate variability, and two-years mortality in patients after myocardial infarction

Sympathetic overactivity and low parasympathetic activity is an autonomic d ysfunction (AD) which enhances cardiac mortality. In the present study, the impact of AD on the mortality in patients after myocardial infarction was evaluated. We examined 162 patients 7-21 days after myocardial infarction, 20 patients of whom died in the course of two years. Baroreflex sensitivity (BRS) was estimated by spectral analysis of spontaneous fluctuations of sy stolic blood pressure and cardiac intervals (Finapres, 5 min recording, con trolled breathing 20/min). The heart rate variability was determined as SDN N index (mean of standard deviations of RR intervals for all 5-min segments of 24-hour ECG recordings). BRS < 3 ms/mm Hg and/or SDNN index < 30 ms wer e taken as markers of AD. The risk stratification was performed according t o the number of the following standard risk factors of increased risk of ca rdiac mortality (SRF): ejection fraction < 40%, positive late potentials an d the presence of ventricular extrasystoles > 10/h. No difference in mortal ity between patients with AD (4%) and without AD (4.5%) was found in 92 pat ients without SRF, the mortality in 6 patients with three SRF was 66.6 %. F ive of these patients had AD. Out of 64 patients with one or two SRF, 32 ha d AD. The mortality of patients without AD was 6.25% and 31.2% of those wit h AD (p<0.025), It is concluded that AD enhanced two-years mortality five f old in our patients with moderate risks.