Coronary cross-sectional area stenosis severity determined using coronary CT highly correlated with coronary functional flow reserve: a pilot study

Fractional flow reserve (FFR) is the gold standard for assessing the physiological significance of coronary stenosis. We examined the potential correlation between digitally measured coronary cross-sectional area stenosis using coronary computed tomography (CT) angiography and FFR. We analyzed data of 32 consecutive patients with stenoses who underwent invasive FFR determination. The cross-sectional area was assessed using 128-slice coronary detector-based spectral CT angiography. Power analysis revealed that the sample size enabled the detection of an area under the receiver operating characteristic (ROC) curve (AUC) of 0.90. FFR ≤ 0.8 and > 0.8 were defined as FFR-positive and FFR-negative, respectively. Intra- and interobserver differences were negligible. Percentage cross-sectional area stenosis was calculated as 100 × (A−B)/A, where A is the cross-sectional area at non-stenotic pre-stenotic segment and B is the cross-sectional area of the most severe stenotic lesion. AUC indicated that percentage cross-sectional area stenosis effectively discriminated between FFR-positive and FFR-negative cases, yielding a sensitivity of 0.882 and specificity of 0.933 at a cutoff of 50% area reduction, with an AUC of 0.976. Lesions with less than 45% cross-sectional area stenosis on coronary CT angiography were not FFR-positive. When ROC analysis was conducted for lesion characteristics, AUC did not significantly improve. In conclusion, the percent coronary cross-sectional area stenosis measured using coronary CT angiography distinguished between FFR-positive and FFR-negative lesions with high accuracy. The severity of coronary cross-sectional area stenosis determined using CT angiography is clinically useful for predicting FFR.