Left main coronary artery stenosis assessment on coronary CT angiography

Assessment of Left Main Coronary Artery (LMCA) stenosis is critical due to its prognostic significance. LMCA cross-sectional area in Coronary Computed Tomography Angiography (CCTA) can provide a non-invasive alternative, but data on its correlation with IVUS remain limited, particularly in different ethnic groups. This study aimed to evaluate CT LM-CSA in determining significant left main stenosis compared to IVUS-MLA in Iranian patients.

We included patients who underwent IVUS for LM stenosis evaluation and had CCTA performed within a maximum of 90 days before IVUS. LM-CSA measured at the narrowest segment on CCTA and MLA obtained via IVUS. Correlation assessed using Pearson's coefficient; agreement evaluated with Bland-Altman analysis. Receiver operating characteristic (ROC) analysis determined the optimal LM-CSA cut-off.

Forty-five patients were included (mean age 59.2 ± 10.1 years; 60% male). IVUS-defined significant LMCA stenosis (MLA <6.0 mm²) was present in 33.3% patients. Baseline characteristics were similar between groups. CCTA-derived LM-CSA showed a strong correlation with IVUS-derived MLA (r = 0.93, p < 0.001). A CT-derived LM-CSA cut-off of 6.2 mm² identified for predicting significant stenosis, yielding 95.6% diagnostic accuracy and an AUC of 0.94 (95% CI: 0.86-1.00), with sensitivity of 88.2% (95% CI: 63.6-98.5%), specificity of 100% (95% CI: 87.7-100%), positive predictive value of 100% (95% CI: 78.2-100%), and negative predictive value of 93.3% (95% CI: 77.9-99.2%).

CCTA LM-CSA is a reliable non-invasive metric for LMCA stenosis assessment. The optimized cut-off provides a threshold derived in an Iranian cohort that requires further validation before it can be used to guide deferral of invasive procedures.