EFFECT OF INTRAVENOUS PROPRANOLOL ON CORONARY VASOMOTION AT REST AND DURING DYNAMIC EXERCISE IN PATIENTS WITH CORONARY-ARTERY DISEASE

Coronary vasomotion was studied at rest and during bicycle exercise with biplanar quantitative coronary arteriography in 28 patients with coronary artery disease. Patients were divided into two groups; the first 18 patients served as controls (group 1), and the next 10 patients were treated with propranolol 0.1 mg/kg, which was infused intravenously before exercise (group 2). Luminal area of a normal and a stenotic vessel segment was determined at rest, during supine bicycle exercise, and 5 minutes after sublingual administration of 1.6 mg nitroglycerin after exercise. In group 1, the normal vessel showed vasodilation (+16%, p < 0.001) during exercise, whereas the stenotic vessel segment showed vasoconstriction (-31%, p < 0.001). After sublingual administration of nitroglycerin, there was coronary vasodilation of both normal (+36%, p < 0.001 vs rest) and stenotic (+20%, p < 0.001) vessel segments. Patients with angina pectoris during supine exercise (n = 10) had significantly (p < 0.05) more vasoconstriction (-36%) than patients without angina (-23%). In group 2, intravenous administration of propranolol at rest was associated with a decrease in luminal area of both normal (-24%, p < 0.001) and stenotic (-43%, p < 0.001) vessel segments; however, during subsequent exercise, both normal (-2%, p = NS vs rest) and stenotic (-3%, p = NS vs rest) vessel segments dilated when compared with the measurements after propranolol. Administration of nitroglycerin further increased luminal area of both vessel segments (normal segment, +23%, p < 0.001; stenotic segment, +46%, p < 0.001 vs rest). It is concluded that dynamic exercise in patients with coronary artery disease is associated with coronary vasodilation of the normal and vasoconstriction of the stenotic coronary arteries. Patients with exercise-induced angina had significantly more stenosis vasoconstriction than patients without angina although minimal luminal area at rest was similar. Intravenous administration of propranolol is accompanied by a significant decrease in coronary luminal area of both normal and stenotic vessel segments at rest, which is overridden by dynamic exercise and sublingual nitroglycerin. The reduction in myocardial oxygen consumption and the prevention of exercise-induced stenosis vasoconstriction might explain the beneficial effect of β-blocker treatment in most patients with coronary artery disease.