THE VARIABLE EXTENT OF JEOPARDIZED MYOCARDIUM IN PATIENTS WITH SINGLE VESSEL CORONARY-ARTERY DISEASE - QUANTIFICATION BY TL-201 SINGLE PHOTON-EMISSION COMPUTED-TOMOGRAPHY

To assess the extent of jeopardized myocardium in patients with single vessel coronary artery disease of variable severity and location, quantitative exercise thallium-201 single photon emission computed tomography was performed in 158 consecutive patients with angiographically proved single vessel coronary artery disease. The extent of abnormal left ventricular perfusion was quantified from computer-generated polar maps of three-dimensional myocardial radioactivity. Patients with only a moderate (51% to 69%) stenosis tended to have a small perfusion defect irrespective of the coronary artery involved. Whereas a perfusion defect measuring greater-than-or-equal-to 10% of the left ventricle was found in 78% of patients with no prior infarction and severe (greater-than-or-equal-to 70%) stenosis, this was observed in only 24% of patients with moderate stenosis. Perfusion defect size increased with increasing severity of stenosis for the entire group without infarction and for those with left anterior descending, right and circumflex coronary artery stenosis. However, the correlation between stenosis severity and perfusion defect size was at best only modest (r = 0.38, p = 0.0001). The left anterior descending artery was shown to be the most important of the three coronary arteries for providing left ventricular perfusion. Proximal stenosis of this artery produced a perfusion defect approximately twice as large as that found in patients with a proximal right or circumflex artery stenosis. However, marked heterogeneity in perfusion defect size existed among all three vessels despite comparable stenosis severity. This was most apparent for the left anterior descending coronary artery, where mid vessel stenosis commonly produced a perfusion defect similar in size to that found in proximally stenosed vessels. In conclusion, single vessel coronary artery disease is a markedly heterogeneous condition with regard to the extent of jeopardized myocardium, which cannot be determined from coronary angiographic information alone. The complementary data obtained by combining the results of both scintigraphic and angiographic studies should improve the precision of clinical decision making when considering the alternatives of pharmacologic or invasive management of single vessel coronary artery disease.