[Coronary vasomotor activity; its significance for the therapy of angina pectoris]

Using quantitative biplane coronary arteriography, coronary vasomotion of normal and stenotic coronary artery segments was studied at rest and during supine bicycle exercise in 37 patients with coronary artery disease. Normal coronary arteries showed vasodilation during exercise, whereas stenotic arteries exhibited vasoconstriction. The occurrence of coronary stenosis narrowing during exercise can be explained either by a collapse of the free vessel wall due to an increase in coronary blood flow velocity (Venturi mechanism) or by insufficient production of the endothelium-derived vasorelaxing factor (endogenous nitrate). To explore further the nature of exercise-induced vasoconstriction of stenotic coronary arteries, intracoronary nitroglycerin, diltiazem or propranolol was given to a subgroup of patients prior to the exercise test. Administration of intracoronary nitroglycerin or diltiazem prevented exercise-induced vasoconstriction, probably due to the direct vasorelaxing effect of the drug on the smooth vasculature. Intracoronary administration of propranolol also prevented exercise-induced vasoconstriction, either due to a reduction in trans-stenotic pressure gradient (local beta blockade with a decrease in local coronary blood flow or an increase in distal arteriolar tone due to unopposed alpha-constrictor tone) or because of a local anesthetic effect of propranolol with a decrease in calcium influx into the smooth vasculature.