Comparison of Anatomical and Physiological Indices of Angiographically Intermediate Left Main Coronary Artery Stenoses

Although physiologic evaluation (e.g., fractional flow reserve) of intermediate lesions is well established in other coronary arteries, the left main coronary artery (LMCA) exhibits diagnostic challenges, hindering development of physiology-based decision-making algorithms. The aim of this study is to evaluate the relationship between angiographic stenosis severity (diameter stenosis, DS%), lesion location and morphologic characteristics and gold-standard pressure indices in patients with intermediate LMCA stenosis. We analyzed 34 patients with angiographically intermediate (25%–65%) LMCA stenosis who underwent intravascular ultrasound (IVUS) imaging and pressure wire assessment. Plaque burden, minimal lumen area (MLA), lesion location, and calcification were documented, and their relationships with FFR and iFR were evaluated. The iFR (r = -0.507 p < 0.001) and FFR (r = -0.383 p = 0.002) were only moderately correlated with DS%. FFR (r = 0.835, p < 0.001) and iFR (r = 0.769, p < 0.001) were significantly correlated with MLA. Presence of calcification partially blunted the correlation between structural and functional parameters. The receiver operating characteristic (ROC) curve showed the highest area under the curve (AUC) for FFR in detecting an MLA<6 mm², with a negative predictive value (NPV) of 80% and a positive predictive value (PPV) of 100%. All lesions with an MLA<6mm² (n = 16) had an FFR <0.80 whereas iFR >0.89 deferred 37% of these lesions. In conclusion, angiographic percent stenosis is an unreliable indicator of hemodynamic significance in intermediate LMCA disease; given that iFR has a high false-negative rate for lesions with MLA <6 mm² despite correlating with MLA, FFR may therefore be a more suitable index for evaluating intermediate LMCA stenoses, and further studies should refine cutoffs for nonhyperemic indices and investigate their clinical implications.