Diagnostic accuracy of single photon emission computed tomography with thallium-201 for the identification of diseased coronary arteries. Comparison between dipyridamole infusion and exercise stress test.

Myocardial perfusion imaging with 201Tl and single-photon emission computed tomography (SPECT) was carried out in two groups of patients, subsequently submitted to diagnostic coronary angiography. SPECT was performed in group 1 (41 patients) after slow i.v. infusion of dipyridamole and in group 2 (162 patients) after tracer injection at maximal ergometric exercise. To evaluate the diagnostic capability of SPECT in the detection of diseased coronary vessels, the left ventricular myocardium was subdivided into 6 segments related to the three major coronary arteries. Sensitivity for the left anterior descending artery was 77% in group 1 and 79% in group 2; specificity was 80% and 96%, respectively. Sensitivity for the right coronary artery was 91% in group 1 and 85% in group 2; specificity was 81% and 73%. For the left circumflex artery sensitivity was 65% for group 1 and 67% for group 2, while specificity was 89% and 88%, respectively. Myocardial SPECT results after ergometric exercise and dipyridamole infusion turned out to be almost superimposable. Dipyridamole stress might be considered appropriate as a provocative test when physical exercise cannot be carried out.