Enhancement of constrictor response of spastic coronary arteries to acetylcholine but not to phenylephrine in patients with coronary spastic angina.

This study examined the direct response of smooth muscle of coronary spasm sites to alpha1-adrenergic stimulation in patients with coronary spastic angina. Phenylephrine (1 microM in the coronary circulation, for 5 min), a stimulator of alpha1-adrenoreceptors, was directly infused into coronary arteries with spasm in 10 patients with coronary spastic angina and into normal coronary arteries in 10 control patients. The luminal diameter of epicardial coronary arteries was determined by computer-assisted quantitative angiography. The constrictor response to intracoronary injection of acetylcholine (ACh; 50 microg) was greater in spastic arteries than in control arteries (decrease from baseline, 48+/-2% vs. 12+/-2%, respectively; p<0.001). ACh (50 or 100 microg) induced coronary spasm associated with myocardial ischemia in all of patients with coronary spastic angina but not in any control patients. On the other hand, phenylephrine infusion did not induce coronary spasm in any of patients with coronary spastic angina or in control subjects. The constrictor response to phenylephrine infusion was comparable between spasm and control coronary arteries (decrease from baseline, 11+/-2% vs. 9+/-2%, respectively; p = NS). The results indicate that smooth muscle of spastic coronary arteries does not exhibit enhancement of constrictor response to direct stimulation of alpha1-adrenoreceptor on coronary smooth muscle. There may be receptor-specific enhancement of constrictor response to agonists in smooth muscle of spastic coronary arteries in patients with coronary spastic angina.