SUMMARY Changes in coronary arterial size due to ergonovine maleate are described and quantitated in 90 patients -18 with typical angina pectoris, 56 with atypical chest pain, nine with variant angina pectoris, and seven heart transplant (allograft) recipients. We observed two angiographic changes in the diameter of coronary arteries: 1) spasm, which was characterized by occlusion or marked (>85%) focal or diffuse vessel narrowing, or 2) relatively mild and diffuse vessel narrowing, which was interpreted as the normal pharmacologic response to the drug. Serial bolus injections of 0.05 mg, 0.10 mg and 0.25 mg of ergonovine maleate produced diffuse narrowing of the diameter of coronary arteries of 10 ± 1.5%, 16 ± 1.4% and 20 ± 1.3% (mean ± SEM), respectively, in the 72 patients with anginal syndromes who did not develop coronary spasm. The degree of coronary arterial narrowing was the same in heart transplant recipients and in patients with normally innervated hearts who did not develop coronary spasm. We believe the normal pharmacologic response to ergonovine maleate was due to a direct vasoconstrictor action of the drug; this action was independent of neural control extrinsic to the heart. CORONARY ARTERIAL SPASM is recognized as a cause of angina pectoris. In attempts to identify patients with this condition, various pharmacologic agents, including methacholine," 2 epinephrine,2 propranolol,2 and ergonovine maleate (EM),3 have been used to provoke coronary vasospasm during coronary arteriography. EM has been shown to induce coronary artery spasm at sites where spontaneous spasm was observed3' 5, 8 and vasospastic coronary artery disease has been demonstrated during coronary angiography by administering this drug. In this study we describe and quantitate the changes in coronary arterial diameter produced by EM when given to patients with various anginal syndromes. In addition, EM was given to heart transplant (allograft) recipients in an attempt to define the mechanism by which this drug affects coronary arterial size. would be given a drug that produced marked coronary artery narrowing which appeared to explain the cause of chest pain in some patients. Patients were told that we expected the results of the study to yield information that would be helpful in their medical treatment. The 90 patients studied included 47 men and 43 women ranging in age from 25-75 years (mean age 48 years). Eighty-three patients were given EM to determine if their anginal syndromes were related to coronary artery spasm. Eighteen of these 83 had typical angina pectoris produced by exercise and relieved by rest or nitrites. Fitly-six patients had chest pain that was not predictably related to stress or relieved by rest or nitrites, and at the time of study we did not know if their pain was cardiac in origin. Nine patients had variant angina pectoris, characterized by nonexertional chest pain that frequently occurred at night and was accompanied by ST-segment elevation. EM was also given to seven clinically stable heart transplant (all...