Workstation-Based Calculation of CTA-Based FFR for Intermediate Stenosis

Abstract

Objectives: This study sought to evaluate the proportion of patients with intermediate coronary stenosis diagnosed on computed tomography angiography (CTA), which may be saved from any further testing due to use of CTA-based fractional flow reserve (FFR).

Background: Coronary CTA often results in diagnosis of intermediate stenosis, triggering further physiological testing. CTA-based FFR (CTA-FFR) is a promising diagnostic tool, which may obviate the need for further testing. However, the specific thresholds for CTA-FFR values predicting ischemic versus nonischemic FFR with acceptable confidence are unknown, obscuring clinical utility of the diagnostic strategy using CTA-FFR.

Methods: We analyzed 96 lesions (mean CTA stenosis: 69.7 ± 11.7%) in 90 patients (63.4 ± 8.2 years, 32% were men) who underwent CTA for suspected CAD and were diagnosed with at least 1 intermediate coronary stenosis (50% to 90%) scheduled for further physiological testing. All patients underwent routine invasive FFR and CTA-FFR evaluation. The objective was to determine the proportion of patients falling between the lower and upper CTA-FFR thresholds that predict ischemic and nonischemic stenosis, respectively (on the basis of an invasive FFR cutpoint of ≤0.80), with ≥90% accuracy.

Results: The invasive FFR ≤0.8 was observed in 41 of 96 lesions (42.7%). According to Bland-Altman analysis, the CTA-FFR underestimated FFR by 0.01 and the 95% limits of agreement were ±0.19. Receiver-operating characteristic area under the curve was significantly higher for CTA-FFR than that for CTA (per lesion 0.835 vs. 0.660, respectively; p = 0.007). The CTA-FFR thresholds for which the positive and negative predictive values were each ≥90% (corresponding to an FFR of ≤0.80) were >0.87 or <0.74, respectively, encompassing 49 lesions (51%) and 45 of 90 patients.

Conclusions: In around one-half of the patients diagnosed with intermediate stenosis, coronary CTA-based FFR may confidently discriminate between ischemic versus nonischemic stenoses. Our findings require validation in an independent cohort.

Keywords: computed tomography angiography; coronary artery disease; fractional flow reserve; functional testing.