Coronary CT Angiography-based Morphologic Index for Predicting Hemodynamically Significant Coronary Stenosis

Purpose To develop a new coronary CT angiography (CCTA)-based index, α×LL/MLD⁴, that considers lesion entrance angle (α) in addition to lesion length (LL) and minimal lumen diameter (MLD) and to evaluate its efficacy in predicting hemodynamically significant coronary stenosis compared with invasive coronary angiography (ICA)-derived fractional flow reserve (FFR). Materials and Methods This prospective study enrolled participants (September 2016-March 2020) from two centers who underwent CCTA followed by ICA (ClinicalTrials.gov identifier: NCT03054324). CCTA images were processed semiautomatically to measure LL, MLD, and α for calculating α×LL/MLD⁴. Diagnostic performance and accuracy of α×LL/MLD⁴ and LL/MLD⁴ in detecting hemodynamically significant coronary stenosis were compared against the reference standard (invasive FFR ≤ 0.80). Results In total, 133 participants (mean age, 63 years ± 9 [SD]; 99 [74%] men) with 210 stenosed coronary arteries were analyzed. Median α×LL/MLD⁴ was 54.0 degree/mm³ (IQR, 25.3-128.7) in participants with invasive FFR of 0.80 or less and 6.7 degree/mm³ (IQR, 3.3-12.8) in participants with invasive FFR of more than 0.80 (P < .001). The per-vessel accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for discriminating ischemic lesions were 86.2%, 83.1%, 88.4%, 84.1%, and 87.7% for α×LL/MLD⁴ and 80.5%, 66.3%, 90.9%, 84.3%, and 78.6% for LL/MLD⁴, respectively. Area under the receiver operating characteristic curve for discriminating hemodynamically significant stenosis was 0.93 for α×LL/MLD⁴, which was significantly greater than the values of 0.84 for LL/MLD⁴ and 0.63 for diameter stenosis (both P < .001). Conclusion The new morphologic index, α×LL/MLD⁴, incorporating lesion entrance angle achieved higher diagnostic performance in detecting hemodynamically significant lesions compared with diameter stenosis and LL/MLD⁴. Keywords: CT Angiography, Cardiac, Coronary Arteries, Ischemia, Infarction, Technology Assessment Clinical trial registration no. NCT03054324 Supplemental material is available for this article. © RSNA, 2023 See also the commentary by Fairbairn and Nørgaard in this issue.