Circadian variation of autonomic nervous activity in patients with multivessel coronary spasm

The present study investigated whether the circadian rhythm of sympathovaga l activity is related to the severity of coronary spasm or multivessel coro nary spasm. Heart rate variability was examined in 22 consecutive patients with vasospastic angina provoked by intracoronary injection of acetylcholin e, who had either multivessel spasm (Group M, n=11) or single vessel spasm (Group S, n=11), in 20 subjects without coronary artery disease (Group C) a nd 20 patients with effort angina who had organic coronary artery stenosis (Group E). The frequency domain indices were analyzed, including low freque ncy (LF: 0.04-0.15Hz) and high frequency (HF: 0.15-0.4Hz), the latter being an index of efferent parasympathetic activity, and the ratio (LH) as an in dex of sympathovagal balance. The circadian variation of the parameters was analyzed by its pattern and was quantified by the difference of the mean v alues between daytime and nighttime. Although the HF power increased during nighttime in Groups C and S, this increase was attenuated in Groups E and M. The circadian variation of the UH ratio (ie, a drop during nighttime) wa s smaller in the S and M groups than in Groups C and E. Accordingly, in Gro up M, the circadian variation of both sympathetic and parasympathetic nervo us activity was attenuated, but in Group S, the variation of sympathetic ne rvous activity, but not parasympathetic nervous activity, was decreased. Th ese data suggest that relatively enhanced sympathetic nervous activity at n ight may be involved in the mechanism underlying multivessel coronary spasm .