Abnormal myocardial blood flow distribution in patients with angina pectoris and normal coronary arteriograms

To evaluate coronary microvascular function and its relation to the genesis of chest pain and ST-segment depression during exercise in patients with s yndrome X, pacing-induced changes in transmural myocardial blood flow distr ibution were quantitatively assessed by 2-dimensional myocardial contrast e chocardiography. Of 25 patients with a history of chest pain and normal cor onary arteries with the negative ergonovine test, 11 had exercise-induced c hest pain and ST-segment depression (syndrome X), and 14 did not (controls) . Myocardial blood flow distribution before and after pacing stress was ass essed by measuring the ratio of the endocardial to epicardial gray level (i e, endo/epi gray level ratio) in the territory of the left anterior descend ing coronary artery. Pacing induced chest pain and ST-segment depression we re observed in syndrome X, but not in controls. The endo/epi gray level rat io in syndrome X significantly decreased after pacing (from 0.98+/-0.10 to 0.76+/-0.17, p<0.01), but not in controls (from 0.97+/-0.08 to 0.99+/-0.08, NS). Abnormal myocardial blood flow distribution may play an important rol e in exercise-induced chest pain and ST-segment depression in these patient s.