Diagnostic value of coronary transluminal attenuation gradient in coronary CT Angiography to assess the severity of stenosis

Abstract

Background: Despite vast technological improvement in recent years, accurate determination of severity of coronary artery stenosis by Coronary CT angiography (CTA) is challenging especially in the case of complex or calcified coronary lesions. Transluminal attenuation gradient (TAG) is a recently developed process which can determine the severity of coronary artery stenosis by measurement of contrast attenuation drop-off along the length of coronary artery. Given the relative paucity of studies in this area, and possible considerable effect on clinical practice, we aimed to evaluate the accuracy of TAG method for determining stenosis severity of coronary arteries in Iranian population. Material and Methods: 82 consecutive patients suspected of having coronary artery disease who underwent 64-slice MSCT coronary angiography and conventional angiography were recruited. Then TAG determined from the change in Hounsfield unit (HU) per 5-mm length of coronary artery and defined as the linear regression coefficient between intra-HU and length from the ostium (millimeters). The diagnostic performance of TAG for detection of significant stenosis was determined and compared by the area under the receiver operating characteristic (ROC) curve. Result: Of the 82 patients; 49 (60) were male and 33 (40) were female. The mean age of the study population was 56.4 years old. The average value of TAG was -2.87. The TAG was significantly different between patients with significant, and non-significant coronary stenosis (PV<0.0001). The study revealed that all patients with TAG value of lower than -5.55 have significant coronary stenosis. The cut off value was determined -3.56. There was not significant relationship between severity of stenosis and the composition of plaques. There was no significant difference in performance of TAG between patients with soft and calcified plaques (PV=0.260). Conclusion: The present study confirms that TAG is the accurate and noninvasive functional method to determine the significant coronary artery stenosis and appears to be able to contribute to improved classification of coronary artery stenosis severity, especially in severely calcified lesions.