Value of transluminal attenuation gradient of stress CCTA for diagnosis of haemodynamically significant coronary artery stenosis using wide-area detector CT in patients with coronary artery disease: Comparison with stress perfusion CMR

Introduction: This study aimed to evaluate the value of transluminal attenuation gradient (TAG) of stress coronary computed tomography angiography (CCTA), using a widearea detector CT in patients with coronary artery disease, compared to stress perfusion cardiac magnetic resonance (CMR) imaging. Methods: This prospective study from May 2012 to January 2015 included 21 patients with moderate coronary stenosis on invasive coronary angiography. All patients underwent adenosine stress single-shot CCTA with a rest CCTA scan using a wide-area detector CT. Coronary artery stenosis was evaluated on both stress and rest CCTA images, and TAG was manually obtained for all vessels. Stress perfusion CMR was used as a reference standard. A TAG cut-off value of-15.1 HU/10 mm was applied for diagnosing haemodynamically significant stenosis. The diagnostic accuracies of TAG and CMR were estimated and compared. Results: TAG of stress CCTA in all coronary arteries had a sensitivity, specificity, and positive and negative predictive values of 90.5, 90.0, 86.4 and 93.1%, respectively. Corresponding values for TAG of rest CCTA in all coronary arteries were 42.9, 83.3, 64.3 and 67.6%, respectively, whereas those for TAG of coronary arteries with moderate stenosis on stress CCTA were 93.3, 100, 100 and 92.3%, respectively. Mean effective radiation doses for stress and rest CCTA were 10.6 ± 2.6 mSv and 2.3 ± 1.3 mSv, respectively. Conclusions: TAG of CCTA provided high diagnostic accuracy for detecting haemodynamically significant coronary artery stenosis. TAG of stress CCTA was more diagnostically accurate, especially in coronary arteries with moderate stenosis.