Evaluation of stenosis severity of coronary calcified lesions using transluminal attenuation gradient: clinical application of 320-row volume CT

BACKGROUND: The aim of this study was to evaluate the accuracy of transluminal attenuation gradient (TAG) in diagnosing the stenosis degree of difficult lesions to accurately assess the degree of luminal stenosis using coronary computed tomography angiography (CCTA). METHODS: A total of 130 patients consecutively received CCTA and coronary angiography (CAG). The average transluminal Hounsfield units (HU) of the regions of interest were consecutively measured at an interval of 5 mm from the ostium to the distal level, followed by the calculation of TAG. The diagnostic performance of CCTA, TAG and CCTA+TAG for the stenosis degree of coronary calcified lesions and their reclassification for stenosis degree were analyzed, especially for calcified lesions. RESULTS: Compared with CAG, the TAG in CCTA was consistent with the largest stenosis degree of each blood vessel. TAG improved the accuracy of CCTA in the diagnosis of calcified lesions (P<0.0001). When threshold was <=-6.9 HU/10 mm, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CCTA+TAG in the diagnosis of coronary calcified lesions were 90.26%, 95.45%, 98.58% and 73.68%. TAG for calcified lesions had moderate sensitivity (86.61%; 95% CI: 81.8-90.5%) and high specificity (91.20%; 95% CI: 84.8-95.5%). In addition, TAG can help to improve the reclassification of CCTA for coronary stenosis degree, especially for calcified lesions (NRI=0.127, P= 0.045). CONCLUSIONS: TAG can help to improve the diagnostic performance of CCTA for the stenosis degree of lesions, and it may also help to improve the reclassification of the stenosis degree of calcified lesions.