VARIABILITY OF NORMAL CORONARY ANATOMY - IMPLICATIONS FOR THE INTERPRETATION OF THALLIUM-SPECT MYOCARDIAL PERFUSION IMAGES IN SINGLE-VESSELDISEASE

Standard criteria for assigning perfusion defects to a specific vascul ar territory often result in mistaken identification of the affected c oronary artery due to the normal variability of coronary anatomy. A re trospective study was performed to determine the frequency of this typ e of error and to identify the most common perfusion patterns associat ed with specific coronary lesions. Methods: Records were reviewed of a ll patients with single-vessel coronary artery disease (CAD) who had e xercise or dipyridamole thallium SPECT myocardial perfusion studies si nce 1987. Patients with coronary artery bypass grafts and an interval between the two studies greater than 6 wk or interval change in medica l status were excluded. Ninety-three studies were available for review . The size, severity and location of all perfusion defects were noted by three observers who had no knowledge of the angiographic data. Sign ificant CAD was defined as luminal diameter stenosis greater than 50%. Results: The diseased vessel was correctly identified in 85% of posit ive studies. Thallium SPECT, however, mistakenly predicted additional vessel involvement in 29% of those studies. Another 15% correctly pred icted single-vessel disease but identified the wrong artery. Using sta ndard criteria, thallium SPECT correctly predicted the arteriogram fin dings in only 56% of studies. Most of these findings could be correlat ed with variations in individual coronary anatomy. Conclusion: The acc urate localization of coronary stenoses by thallium SPECT imaging requ ires close correlation with arteriography owing to the significant var iability in normal coronary anatomy.