309 Computed Tomography Coronary Angiography for the Assessment of Left Main Coronary Artery Stenosis.

Background: Angiographic assessment of left main coronary artery (LMCA) stenosis is challenging. When uncertainty exists, intravascular ultrasound (IVUS) minimal lumen area (MLA) >=6 mm2 is used as safe threshold for deferral of revascularization. With emergence of Computed Tomography Coronary Angiography (CTCA) as a first-line investigation, we sought to assess which quantitative CT-measure best compared with current IVUS standards. Method(s): Patients who underwent both IVUS and CTCA assessment of angiographically intermediate LMCA stenosis (n=48) were included. All CTCA were performed <90 days prior to IVUS. The cohort was divided into those with significant (S-LMCA) versus non-significant (NS-LMCA) disease, using IVUS >=6 vs <6 mm2. Result(s): Mean age (60.3+/-12.4 vs 59.9+/-11.9yrs, p=0.91) and % male (57.7% vs 54.6%, p=0.83) were similar between groups. Mean time from CTCA to IVUS assessment was 17.4+/-19.8 days, with mean QCA stenosis severity of 46.0+/-18.6%. On CTCA, patients with NS-LMCA had significantly higher luminal area (8.3+/-3.8 vs 5.2+/-1.6 mm2, p=0.005), minimal lumen diameter (MLD) (3.2+/-0.7 vs 2.5+/-0.4 mm, p<0.001), with similar luminal volumes (99.9+/-50.5 vs 113.5+/-73.9 mm3, p=0.47). There was a significant positive correlation between CTCA and IVUS MLA (r=0.77, p <0.001) and MLD (r=0.73, p<0.001). ROC analysis demonstrated CTCA MLA <8.29 mm2 had the best diagnostic accuracy for predicting IVUS MLA <6 mm2 (area under the curve=0.76, sensitivity=100%, specificity=54% p=0.002). Conclusion(s): CTCA luminal measures correlate well with IVUS within the LMCA. These results suggest that CTCA measures could potentially be used to safely defer revascularisation for LMCA disease.Copyright © 2020