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

Abstract

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. 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. 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). 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.