Objectives. This study investigated whether insulin response to an oral glucose load correlates to acetylcholine-induced coronary vasoconstriction in subjects with vasospastic angina.
Background. It has been suggested that coronary vasospasm is caused by augmented vascular responsiveness possibly exerted by atherosclerosis. Recently, insulin resistance syndrome has been proposed as a major promotor of atherosclerotic disease, potentially enhancing vascular smooth muscular tone.
Methods. Among subjects with angiographically smooth coronary arteries, we selected 14 subjects with vasospastic angina and 14 age- and gender-matched subjects with atypical chest pain. We compared coronary vasomotor response to acetylcholine infusion, glucose and insulin responses to an oral glucose load (75 g), serum lipid concentrations, obesity, heart rate, blood pressure and smoking habits in both groups.
Results. Fasting serum insulin concentrations and insulin response were higher in subjects with vasospastic angina than in those with atypical chest pain; however, glucose tolerance, obesity, heart rate, blood pressure and smoking habits did not differ between groups. In subjects with vasospastic angina, nearly all coronary segments, except distal segments of the left circuraflex coronary artery, were constricted at peak acetylcholine infusion (20 to 100 μg), whereas all segments were dilated in subjects with atypical chest pain. Regression analysis for both groups demonstrated a correlation between coronary vasoconstriction and fasting serum insulin concentrations (r = 0.52, p < 0.01), insulin response (r = 0.71, p < 0.001), serum triglyceride concentrations (r = 0.51, p < 0.05) and atherogenic index (r = 0.44, p < 0.05).
Conclusions. Results show that acetylcholine-induced coronary vasoconstriction in subjects with vasospastic angina correlates with hyperinsulinemia and enhanced insulin response, suggesting insulin resistance syndrome as a feature of vasospastic angina.
