Background: We investigated whether diffuse coronary vasoconstriction induced by acetylcholine caused myocardial ischemia.
Methods: We studied 30 patients (40 coronary arteries) with spontaneous chest pain or equivocal studies on treadmill exercise testing and no significant coronary stenosis or previous myocardial infarction. During the acetylcholine provocation test, Doppler echocardiography was performed, and thallium-201 was injected intravenously for scintigraphy. We used Doppler echocardiography to measure the ratio of early-to-late peak mitral flow (E:A ratio).
Results: When acetylcholine was injected, the coronary arteries showed three different responses. Diffuse coronary vasoconstriction without chest pain or ischemic changes on the ECG was induced in 18 (45%) arteries and the E:A ratio decreased from 0.83 +/- 0.13 to 0.77 +/- 0.13 (P = 0.031). In 17 vessels (control arteries), the E:A ratio did not change significantly (from 0.88 +/- 0.15 to 0.88 +/- 0.18; P = 0.95). In five arteries, focal spasm was induced and the E:A ratio decreased from 0.83 +/- 0.18 to 0.66 +/- 0.13 (P = 0.043). Transient defects on thallium-201 scintigraphy were observed in the territory of eight (80%) arteries with diffuse vasoconstriction and in one (20%) control artery (P = 0.047).
Conclusions: Diffuse coronary vasoconstriction induced by intracoronary acetylcholine can decrease the regional myocardial blood flow (as shown by thallium-201 scintigraphy) and can cause global left ventricular diastolic dysfunction (as shown by the results of Doppler echocardiography).