Noninvasive Detection of Regional Myocardial Ischemia

The sensitivity of rest and stress myocardial perfusion studies using scintillation camera imaging of intravenously administered rubidium-81 (81Rb) in the detection of myocardial ischemia was compared to that of stress electrocardiography by relating results in 40 patients to the degree of stenosis delineated by coronary arteriography. Of 33 patients with greater than 75% stenosis of at least one of the three major coronary vessels (significant stenosis), rest and stress 8lRb imaging detected ventricular ischemia in 29 (88%), whereas simultaneous stress electrocardiography was positive (1 mm or greater horizontal ST-segment depression) in only 19 (58% ) of the same patients. Five of the 29 patients who developed stress-induced scintigraphic evidence of ischemia did not develop angina or a positive electrocardiogram with stress. In 31 of the 33 patients with significant coronary stenosis, either the stress scintigram or the stress electrocardiogram was positive. In seven patients with less than 50% narrowing of a major coronary vessel on coronary arteriography, the stress scintigrams were negative, whereas the stress electrocardiograms were positive in the two of these patients with the syndrome of angina with normal coronary arteriograms. It is concluded that high resolution images of the myocardium can be obtained with 81Rb using the scintillation camera with special shielding, and that rest and stress 81Rb scintigraphy appears to provide greater sensitivity and specificity when compared to stress electrocardiography in the noninvasive identification of significant coronary stenosis.