AUTONOMIC CHANGES ASSOCIATED WITH SPONTANEOUS CORONARY SPASM IN PATIENTS WITH VARIANT ANGINA

Objectives. This study sought to investigate whether changes in nervou s autonomic tone may have a role in the mechanisms triggering spontane ous coronary spasm in variant angina. Background. Previous studies hav e suggested that both sympathetic and vagal activation may act as a tr igger of epicardial artery spasm in patients with variant angina, but the actual role of autonomic changes in spontaneous coronary spasm rem ains unknown. Methods. We analyzed the changes in heart rate variabili ty associated with episodes of ST segment elevation detected on Holter monitoring in 23 patients,with variant angina (18 men, 5 women; mean [+/-SD] age 59 +/- 12 years). For study purposes, episodes of transmur al ischemia lasting greater than or equal to 3 min and without any ST segment changes in the previous 40 min were selected for analysis. Hea rt rate variability indexes were calculated at 2 min intervals, at 30, 15, 5 and 1 min before ST elevation and at peak ST segment elevation. Ninety-three of 239 total ischemic episodes (39%) fulfilled the inclu sion criteria. Results. The results showed that 1) high frequency (HF) (0.04 to 0.15 Hz), a heart rate variability index specific for vagal activity, decreased in the 2 min preceding ST segment elevation (p < 0 .001) and, returned to basal levels at peak ST segment elevation; 2) h eart I ate and low frequency (0.04 to 0.15 Hz), which are partially co rrelated with sympathetic activity, showed a significant increase at p eak ST segment elevation (p < 0.001 for both); 3) the pattern of the H F reduction before ST segment elevation was consistently confirmed in several subgroups of ischemic episodes, including those of patients wi th or without coronary stenoses, those of patients with anterior or in ferior ST segment elevation, those occurring during daily or nightly h ours and silent episodes, There were no significant variations in hear t rate variability in control periods selected from Holter tapes of pa tients and before ST segment elevation induced by balloon inflation in 20 patients undergoing coronary angioplasty. Conclusions. Our data sh ow that changes in autonomic tone are likely to contribute to trigger or predispose to epicardial spasm. In particular, although not excludi ng an active role for adrenergic mechanisms, our data suggest that a v agal withdrawal may often be a component of the mechanisms leading to spontaneous coronary vasospasm.