Change in heart rate variability preceding ST elevation in a patient with vasospastic angina pectoris

A case of vasospastic angina (VSA) in a 62-year-old man with frequent ST elevation throughout the day was reported. His coronary angiogram showed that intracoronary methylergometrine had induced total occlusion due to a vasospasm. Analysis by Holter monitoring suggested that the autonomic nervous system would contribute differently to the initiation of the coronary spasm depending on whether the VSA attacks occurred during the daytime or at night. During the nighttime, the high-frequency power (HF: 0.15-0.4 Hz) decreased during the 2 min before ST elevation, and the heart rate increased immediately before ST elevation. The low-frequency power (LF: 0.04-0.15 Hz) and the ratio of LF to HF (LF/HF) did not significantly change before ST elevation. In contrast, each of the heart rate variability components and the heart rate did not significantly change before ST elevation during the daytime. Thus, the pathophysiology of VSA during the daytime and nighttime seems to be different in its relation to autonomic tone. During the nighttime, vagal withdrawal may be a component of the mechanisms leading to VSA, while during the daytime, a change in autonomic tone may not play a major role in this case.