Significant stenosis of coronary arteries in patients with single and multiple vessel diseases without previous myocardial infarction.

To determine what degree of stenosis should be counted as a significant lesion in each of 3 major coronary arteries in classification of the number of vessels involved, coronary arteriographic percent diameter narrowing (by quantitative angiography) was compared with thallium-201 scinitgraphic redistribution on treadmill exercise in 47 patients with evidence of exercise myocardial ischemia and greater than or equal to 50% diameter narrowing (visual assessment) in at least 1 major coronary artery. Severity of exercise-induced myocardial ischemia for the entire left ventricle (assessed by averaged redistribution index) was separated most sufficiently with definition of 63-64% or greater between patient groups with no- and single-, single- and double-, and double- and triple-vessel diseases. Collaterals and intraventricular contractile interaction are possibly the factors making definition more severe in extensive coronary artery disease. Since the visual method gives an overestimation of stenosis, it was concluded that vessel diameter narrowing of 70% or more should be regarded as significant in patients with single and multiple vessel diseases if the visual method is used.