RESPONSES OF ANGIOGRAPHICALLY NORMAL HUMAN CORONARY-ARTERIES TO INTRACORONARY INJECTION OF ACETYLCHOLINE BY AGE AND SEGMENT - POSSIBLE ROLE OF EARLY CORONARY ATHEROSCLEROSIS

We examined the response of left coronary arteries to intracoronary injection of acetylcholine (ACh) 50 μg in 74 patients by measuring the diameter changes with a videodensitometric analysis system. Patients with angiographically normal coronary arteries were subdivided into a younger group of 26 patients (age, 9-29 years) and an older group of 23 patients (age, 31-68 years). In the younger group, the diameter at the distal segment of the left anterior descending artery (LAD) and at the proximal, middle, and distal segments of the left circumflex artery (LCx) increased significantly (16.7±19.3%, p<0.01, for LAD and 8.0±18.8%, p;<0.05; 11.0±16.1%, p<0.01; and 19.8±17.5%, p<0.01, for LCx segments, respectively) in response to ACh. In the older group, on the other hand, the diameter at the proximal and middle segments of LAD and LCx decreased significantly (-20.8±16.9%, p<0.01; and -17.9±28.4%, p<0.01, for LAD segments and -14.6±17.4%, p<0.01; and -11.3±21.4%, p<0.05, for LCx segments, respectively). The dilator response to ACh in the younger group was significantly greater in the distal segment than in the proximal segment in both LAD and LCx (p<0.01 for LAD and p<0.05 for LCx). The constrictor response to ACh in the older group was significantly greater in the proximal than the distal segment in both LAD and LCx (p<0.05 for LAD and LCx, respectively). Nearly all coronary arteries with angiographically evident atherosclerosis constricted to ACh in 25 patients. We conclude that most of the angiographically normal coronary arteries in subjects more than 30 years old have endothelial dysfunction or atherosclerosis and that the proximal segment is more prone to atherosclerosis than the distal segment.