Accuracy of angiographic determination of left main coronary arterial narrowing. Angiographic--histologic correlative analysis in 28 patients.

To evaluate the accuracy of coronary angiography in identifying severe narrowing of the left main coronary artery (LMCA), the degree of narrowing observed by angiography was compared to that observed at necropsy in 28 patients with symptomatic coronary heart disease in whom angiography had been performed within 40 days of death. The angiograms were evaluated independently by three experienced angiographers. In 20 of the 28 patients (71%), the degree of narrowing of the LMCA was either underestimated (13 patients) or overestimated (10 patients) by two or three of three angiographers; of 84 angiographic judgments made by the three angiographers in the 28 patients, 54 (64%) were underestimates (33 judgments, 39%) or overestimates (21 judgments, 25%) of the degree of LMCA narrowing. Of 12 LMCAs narrowed 76-100% in cross-sectional area at necropsy, six were underestimated at preoperative angiography by two or three of three angiographers; of 12 LMCAs narrowed 51-75% in cross-sectional area at necropsy, all 12 were either under- or overestimated angiographically by two or three of three angiographers; of four LMCAs narrowed 26-50% in cross-section at necropsy, two were overestimated by two of three angiographers. Thus, angiographic determination of degrees of narrowing of the LMCA during life is subject to considerable error. The angiographic errors appear to have resulted primarily from the presence of atherosclerotic plaque in the LMCA and an insufficient number of angiographic projections.