SPECT Dipyridamole scintigraphy for detecting coronary artery disease in patients with isolated severe aortic stenosis

Abstract

Background: The sensitivity and specificity of non-invasive methods – specifically single-photon emission computed tomography (SPECT) dipyridamole–thallium myocardial perfusion – for detecting coronary artery disease (CAD) in patients with severe aortic stenosis remains unclear. Occasionally, these patients present with atypical angina. Therefore, a CAD diagnosis must be excluded to prevent unnecessary cardiac catheterization. Methods: To determine the diagnostic value of SPECT dipyridamole–thallium imaging in this population, we compared the effectiveness of the imaging procedure with that of coronary angiography by prospectively analyzing patients who underwent both procedures. Group 1 included 59 patients who were asymptomatic or had atypical angina; group 2; 51 preoperative aged-matched patients with typical angina. SPECT acquisition was performed 15 min after 0.142 mg/kg/min of dipyridamole infusion completion, and redistribution images were performed 4 h after thallium injection. Two cut-off values of luminal diameter narrowing, >50 and >70%, defined significant CAD. Results: Coronary angiography with significant CAD (>50%) was present in 15 (25%) group 1 patients and in 16 (32%) group 2 patients (P=NS). The sensitivity was greater in group 2 than in group 1 (56 versus 26%; P=0.001). The specificity, positive and negative predictive value, and accuracy in the groups were similar. CAD of >70% luminal stenosis was present in 11 (19%) group 1 patients and in 12 (23%) group 2 patients (P=NS). The positive predictive value was greater in group 2 than in group 1 (75 versus 43%; P=0.001) but similar sensitivity, specificity, negative predictive value, and accuracy. The likelihood ratio for abnormal test increased in patients with CAD of >70%. Conclusions: symptoms of typical angina had significant impact on test sensitivity, positive predictive value and likelihood ratio for abnormal test. Furthermore, SPECT dipyridamole–thallium imaging was a useful non-invasive method to exclude the diagnosis of significant CAD (high specificity) in asymptomatic and symptomatic patients with isolated severe aortic stenosis.