Autonomic nervous discharge had been implicated in the pathogenesis of coronary artery spasm although the precise mechanisms by which coronary spasm is triggered remain to be elucidated. The purpose of this study was to assess the pattern of the autonomic nervous system in patients with variant angina through the analysis of heart rate variability.

We compared the pattern of cardiac sympathetic and parasympathetic activity through the time domain and frequency domain analysis of heart rate variability with 24-hour Holter monitoring between 14 patients with variant angina and 14 healthy control subjects. None of the patients had organic coronary artery stenosis as determined by angiography.

1) Among the time domain indices, the percent of successive normal NN intervals difference greater than 50 msec (pNN50) and the square root of the mean squared differences of successive NN intervals (rMSSD) in the patient group were significantly lower than those in the normal control (p<0.05, repectively). 2) In the patient group, mean R-R intervals were significantly shortened from night to early morning compared to control group (p<0.05). 3) With frequency domian analysis, low frequency (0.04 to 0.15Hz) spectrum, which is correlated with sympathetic activity, was revealed no significant difference between two groups. From night to early morning, significant increase of high frequency (0.15 to 0.4 Hz) spectrum, which is specific index for vagal activity, and significant decrease of the ratio of low to high frequency, which represents sympatho-vagal interaction, was blunted in the patient group (p<0.05).

In variant angina, cardiac vagal influence on the heart rate was blunted and sympathetic activity was predominant at night and in the early morning.