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 micrograms 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 less than 0.01, for LAD and 8.0 +/- 18.8%, p less than 0.05; 11.0 +/- 16.1%, p less than 0.01; and 19.8 +/- 17.5%, p less than 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 less than 0.01; and -17.9 +/- 28.4%, p less than 0.01, for LAD segments and -14.6 +/- 17.4%, p less than 0.01; and -11.3 +/- 21.4%, p less than 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 less than 0.01 for LAD and p less than 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 less than 0.05 for LAD and LCx, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)