Coronary reserve and exercise ECG in patients with chest pain and normal coronary angiograms

• Published in: Circulation (New York, N.Y.) N.Y.), 1992-07, Vol.86 (1), p.179-186
• Main Authors: CAMICI, P. G, GISTRI, R, LORENZONI, R, SORACE, O, MICHELASSI, C, BONGIORNI, M. G, SALVADORI, P. A, L'ABBATE, A
• Format: Article
• Language: English
• Subjects: Adult; Aged; Biological and medical sciences; Cardiology. Vascular system; Chest Pain - classification; Chest Pain - diagnostic imaging; Chest Pain - physiopathology; Coronary Angiography; Coronary Circulation; Coronary heart disease; Electrocardiography; Exercise Test; Female; Heart; Humans; Male; Medical sciences; Middle Aged; Nitrogen Radioisotopes; Physical Exertion; Reference Values; Tomography, Emission-Computed; Vasodilation - physiology
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/01.CIR.86.1.179

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. We have investigated the correlation between coronary vasodilator reserve, assessed with 13N-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-1.g-1; it increased to 1.32 +/- 0.47 ml.min-1.g-1 (p less than 0.01 versus baseline value) during atrial pacing and to 2.52 +/- 0.96 ml.min-1.g-1 (p less than 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 of 3.02 +/- 0.33 ml.min-1.g-1 after dipyridamole (range, 2.13-5.46 ml.min-1.g-1), and 14 (33%) patients had a mean flow of 1.48 +/- 0.29 ml.min-1.g-1 (range, 1.06-2.04 ml.min-1.g-1, p less than 0.01 versus the "high-flow group"). Approximately one third of patients in our series showed a reduced coronary vasodilator reserve. Although 12 of 14 patients in the "low-flow group" had ST segment depression during exercise stress, 16 of 29 patients in the high-flow group also had ST segment depression during exercise stress. Therefore, despite a good sensitivity (86%) in identifying patients with a blunted increment of coronary flow, the ECG response during exercise stress appears to have a rather low specificity (45%). This suggests that factors other than reduced coronary reserve and myocardial ischemia may play a role in the genesis of the ST segment depression in these patients.