Additional value of thallium-201 SPECT to a conventional exercise test for the identification of severe coronary lesions after an episode of unstable coronary artery disease

The additional value of thallium-201 SPECT to a conventional exercise test for the identification of patients with severe coronary lesions was evaluated in 170 men, one month after an episode of unstable coronary artery disease. Severe coronary lesions at coronary angiography — defined as three vessel disease, left main stenosis or proximal left anterior descending artery stenosis as part of two vessel disease — were observed in 45.9%. In the SPECT image, the left ventricular myocardium was divided into nine segments and each segment was classified as either normal (=0), reduced uptake (=1) or uptake defect (=2). The sum of gradings in all segments post-exercise was denoted SPECT score. The patients were divided into nine different groups regarding ST-depression during exercise (no ST-depression, ST-depression in 1–2 leads or 3 leads) and SPECT score (no SPECT score, 1–3 scores or 4 scores). Severe coronary lesions were, in 68% identified by SPECT score 4 and in 65% by ST-depression in 1 lead at exercise test. The specificity for identification of severe coronary lesions was, for both tests, 65%. SPECT score 4 and/or ST-depression in 3 leads identified 82% of the patients with severe coronary lesions with a specificity of 63%. Furthermore, SPECT score 3 identified more patients with isolated proximal left anterior descending artery stenosis than ST-depression alone at exercise test.