Exclusion of coronary artery disease by exercise thallium-201 tomography in patients with aortic valve stenosis

Abstract

In many patients with valvular aortic stenosis (AS), management decisions may be possible without invasive studies if coexistent coronary artery disease (CAD) can be ruled out noninvasively. The use of thallium-201 single-photon emission computed tomography to the exclusion of CAD was studied in 44 patients aged 41 to 78 years with AS. In addition to cardiac catheterization and selective coronary angiography, patients underwent a cardiac ultrasound study and thallium-201 myocardial perfusion imaging at rest and after bicycle ergometer exercise. Two thirds of the patients had critical AS (valve area index ≤0.5 cm 2/m 2) but none had left ventricular systolic dysfunction. Twenty-one patients had angiographically significant CAD (≥50% diameter stenosis in ≥1 coronary artery), whereas 23 had either a fully normal angiogram (n = 17) or mild (<50%) stenoses (n = 6). Each patient with significant CAD had an abnormal thallium-201 tomogram, either a strictly segmentai perfusion defect (n = 19), or a patchy nonsegmental abnormality (n = 2); however, 10 of 23 patients free of significant CAD had similar results. Thus, the sensitivity and specificity of an abnormal scintigram were 100 and 57%, respectively. If only segmental perfusion defects typical of CAD had been considered abnormal, then the sensitivity of the test would have been 90% and the specificity 70%. Patients with false abnormal scintigrams had more severe AS and more angiographically nonsignificant CAD than those with true normal findings. It is concluded that a fully normal exercise thallium-201 tomogram excludes angiographically significant CAD in patients with AS, and that false-positive findings are related to critical valve area reduction and to the presence of mild coronary stenoses.