Changes in autonomic nervous activity prior to spontaneous coronary spasm in patients with variant angina

Although the autonomic nervous system has been implicated in the genesis of coronary spasm, the precise mechanism by which it serves as the trigger of coronary spasm remains unclear. The aim of this study was to investigate c hanges in autonomic nervous activity associated with ischemic episodes in p atients with variant angina (VA). Heart rate variability (HRV) on Holter mo nitoring was analyzed during 17 ischemic episodes in 11 patients with VA. T he parameters of HRV were measured during a 2-min period at various time in tervals prior to the onset of ST-segment elevation. The low frequency (LF) and high frequency (HF) components of the HRV, LF/HF ratio, mean RR interva l, and the coefficient of the RR interval variation (CV) were calculated fo r each time interval. Both the HF and the CV increased significantly in the 2 min prior to the onset of ST-segment elevation, suggesting heightened va gal activity. The LF/HF ratio, a measure of cardiac sympatho-vagal balance, did not change. The LF, a measure of sympathetic activity with vagal modul ation, also did not change. The RR interval decreased significantly in the 2 min prior to the onset of ST-segment elevation. These results suggest tha t enhancement of both the vagal and the sympathetic nervous activity plays an important role in the initiation of coronary spasm.