Mental stress prebably leads to disease by the effect on autonomic nervous system, especially on cardiovascular nervous system it leads deleterious effects ranging from the apperarence or worsenig of ischemia to lethal arrhythmia or sudden death. Especially after myocardial infarction this risks were increased.

In order to assess the effect of postural change and arithmetic test on the state of autonomic nervous system in patients with AMI(acute myocardial infarction) autoregressive power spectral analyses were applied to 21 healthy subjects(51.9±6.5 years) and 20 AMI patients(55.3±7.4 years) during supine, standing and arithmetic test.

R-R interval and systolic blood pressure decreased during standing compared with during supine position but there were no remarkable changes during arithmetic test compared with during supine position.

In two groups, both during standing and during arithmetic test, compared with during supine position, the remarkable increase of LF(low frequency) spectral parameters(Nu, p<0.001) and decrease of HF(high frequency) spectral parameter(Nu, p<0.001) were observed. And during arithmetic test, compared with during standing, the remarkable increase of LF spectral parameter(Nu, p<0.01) and decrease of HF spectral parameter(Nu, p<0.01) were observed. LF/HF ratio and LFCCV/HFCCV ratio, so an index of sympatho-vagal balance, significantly increased during standing and during arithmetic test compared with during supine position and the increase was more prominent during arithmetic test(p<0.05).

There was no significant difference of spectral parameters beteen two groups.

In conclusion, sympathetic activity increased during standing and during arithmetic test. Especially, during arithmetic test it induced only sympathetic activity to increase remarkably without significant hemodynamic changes. The state of autonomic nervous system 7-10 days after AMI was not different from that of healthy subjects. Among the spectral parameters, Nu was more useful than either PSD or CCV in assessing autonomic nervous activity.