Variable Predictor of Non-Measurability for Fractional Flow Reserve Derived from Coronary Computed Tomography Angiography

Abstract

Abstract Purpose The fractional flow reserve derived from coronary computed tomography angiography (FFRCT) cannot be analyzed in some cases (non-measurability). Current data on non-measurability is lacking. This study aimed to examine the non-measurability rate and factors associated with non-measurability in daily clinical practice. Methods This retrospective observational study included consecutive patients who underwent FFRCT analysis at our hospital. The primary outcome was FFRCT non-measurability (defined as an inability to perform quantitative analysis with FFRCT) rate. Factors associated with non-measurability were evaluated with logistic regression analysis. Results Among the 307 patients enrolled, 21 (6.8%) could not be analyzed. Heart rate at computed tomography examination and coronary calcium scores were significantly higher in cases with non-measurability than in those with measurability (heat rate: 69.6 ± 8.9 bpm vs. 61.0 ± 11.1 bpm; p = 0.001; coronary calcium score; 931.2 [290.8, 1451.3] vs. 322.9 [100.7, 850.0]; p = 0.008). Multivariate analysis showed that heart rate was an independent predictor for non-measurability (odds ratio, 1.05; 95% CI: 1.02, 1.09; p = 0.002). Based on the receiver operating characteristic curve analysis, the optimal cut-off value of heart rate and coronary calcium score is 63 bpm (specificity, 67.1%; sensitivity, 76.2%) and 729.2 (specificity, 71.3%; sensitivity, 66.7%), respectively. In addition, the absence of two features (heart rate > 63 bpm and coronary calcium score > 729.2) showed a high negative predictive value (99.3%) for FFRCT non-measurability. Conclusions The rate of FFRCT non-measurability was 6.8%. Heart rate is an important factor in acquiring FFRCT values and, when combined with coronary calcium score, can predict FFRCT measurability with high probability.