Computed tomography coronary angiography assessment of left main coronary artery stenosis severity

Background: Angiographic assessment of left main coronary artery (LMCA) stenosis severity can be unreliable. In cases of ambiguity, intravascular ultrasound (IVUS) can be utilised with a minimal lumen area (MLA) of >6 mm(2) an accepted threshold for safe deferral of revascularization. We sought to assess whether quantitative computer tomography coronary angiography (CTCA) measures could assist clinicians making LMCA revascularization decisions when compared with IVUS as gold standard. Methods: Consecutive patients undergoing IVUS assessment of angiographically intermediate LMCA stenosis were included. All patients had undergone 320-slice CTCA <90 days prior to IVUS imaging. Offline quantitative assessment of IVUS- and CT-derived measures were undertaken with the cohort divided into those with significant (s-LMCA) versus non-significant (ns-LMCA) disease using the accepted IVUS threshold. Results: Fifty-eight patients were included, with no difference in mean age (61.5 f 12.2 vs. 59.7 f 11.9 years, p = 0.57), diabetic status (24.2% vs 16.0%, p = 0.44) or other baseline demographics between groups. Patients with ns-LMCA had larger CT luminal area (8.64 f 3.91 vs. 5.41 f 1.54 mm2, p < 0.001), larger minimal lumen diameter (MLD) (3.25 f 0.74 vs. 2.56 f 0.38 mm, p < 0.001) and lower area stenosis (45.74 f 18.10 vs. 60.93 f 14.68%, p = 0.001). There was a significant positive correlation between CTCA and IVUS MLA (r = 0.68, p < 0.001) and MLD (r = 0.67, p < 0.001). ROC analysis demonstrated CTCA MLA cut-off <8.29 mm(2) provides the greatest negative predictive value and sensitivity in predicting the presence of significant LMCA disease. Conclusion: CTCA derived MLA and MLD have a strong correlation with IVUS. A CTCA derived MLA cut-off <8.29 mm(2) showed greatest clinical utility for predicting the need for further assessment, based on IVUS gold standard.