Calcific versus non-calcific plaque: a CAD-RADS and FFRCT study

Coronary Artery Disease-Reporting and Data System (CAD-RADS) standardises Computed Tomography Coronary Angiography (CTCA) reporting. Coronary calcification can overestimate stenosis. We hypothesized where CADRADS category is assigned due to predominantly calcified maximal stenosis (Ca+), the CTCA-derived Fractional Flow Reserve (FFRCT) would be lower compared to predominantly non-calcified maximal stenoses (Ca-) of the same CAD-RADS category. Consecutive patients undergoing routine clinical CTCA (September 2018 to May 2020) with ≥1 stenosis ≥25% with FFRCT correlation were included. CTCA's were subdivided into Ca+ and Ca-. FFRCT was measured in the left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA). Potentially flow-limiting classified as FFRCT≤0.8. A subset had Invasive Coronary Angiography (ICA). 561 patients screened, 320 included (60% men, 69±10 years). Ca+ in 51%, 69% and 50% of CAD-RADS 2, 3 and 4 respectively. There was no difference in the prevalence of FFRCT≤0.8 between Ca+ and Ca- stenoses for each CAD-RADS categories. No difference was demonstrated in the median maximal stenoses FFRCT or end-vessel FFRCT within CAD-RADS 2 and 4. CAD-RADS 3 Ca+ had a lower FFRCT (maximal stenosis p= .02, end-vessel p= .005) vs Ca-. No difference in the prevalence of obstructive disease at ICA between predominantly Ca+ and Ca- for any CAD-RADS category. There was no difference in median FFRCT values or rate of obstructive disease at ICA between Ca+ and Castenosis in both CAD-RADS 2 and 4. Ca+ CAD-RADS 3 was suggestive of an underestimation based on FFRCT but not corroborated at ICA.