Coronary Angiograms

Background. Coronary vasodilator reserve is reduced in some patients with a history of chest pain and angiographically normal coronary arteries. ECG changes suggestive of myocardial ischemia during exercise also can be demonstrated in a subset of these patients. Methods and Results. We have investigated the correlation between coronary vasodilator reserve, assessed with "N-labeled ammonia and positron emission tomography, and the ECG during exercise stress in 45 patients with a history of chest pain, angiographically normal coronary arteries, and a negative ergonovine test. ST segment depression on the ECG during exercise was present in 29 of 45 patients. Mean resting left ventricular blood flow was 1.04±0.22 ml' min' g-'; it increased to 1.32±0.47 ml min-l g` (p<0.01 versus baseline value) during atrial pacing and to 2.52±0.96 ml * min'1 * g` (p<0.01 versus baseline value) after dipyridamole (0.56 mg/kg i.v.). No regional flow defects could be demonstrated in any patient during pacing or after dipyridamole. Myocardial flows after dipyridamole, however, did not show a normal frequency distribution (Kolmogorov-Smirnov test), and two patient populations could be identified. Twenty-nine (67%) patients had a mean left ventricular flow of3.02±0.33 ml * min' * g` after dipyridamole (range, 2.13-5.46 ml min' g-'), and 14 (33%) patients had a mean flow of 1.48±0.29 ml ming` (range, 1.06-2.04 ml min-l. g-', p<0.01 versus the "high-flow group"). Conclusions. Approximately one third of patients in our series showed a reduced coronary vasodilator