Prognostic implications of CT-derived FFR in proximal vs. distal coronary segments

Abstract Background CT-derived Fractional Flow Reserve (CT-FFR) allows functional assessment of coronary stenosis based on coronary CT angiography (CCTA). CT-FFR has prognostic relevance for future cardio-vascular events yet it remains unclear whether FFR values in distal coronary segments offer different prognostic insight as compared to CT-FFR values in proximal coronary segments. Methods 563 patients who underwent coronary CT angiography (CCTA) due to suspected CAD were included in this analysis. CT-FFR was measured using prototype software. CT-FFR values were obtained at the proximal and distal end of all coronary segments with a reference diameter ≥ 2mm. On a per-patient level the minimal value (minimal CT-FFR) as well as the maximum drop in CT-FFR (∆CT-FFR) over any one segment was recorded. Coronary segments 1, 2, 5, 6, 11 and 16 were defined as proximal segments, the remaining segments as distal. Patients were followed for major cardiovascular events (non-fatal stroke, non-fatal myocardial infarction, cardiovascular death) and revascularization (PCI or CABG). Results Of 563 included patients (62 ± 11 years, 58% men), 57 (10,1%) experienced MACE and 146 (25,9%) received revascularization during follow up (median 72 ± 18 months). The minimal CT-FFR per patient was 0.80 ± 0.16 (proximal segments 0.87 ± 0.13, distal 0.81 ± 0.15). Mean ∆CT-FFR per patient was 0.14 ± 0.13 (proximal 0.10 ± 0.11, distal 0.10± 0.10). Regarding MACE, the AUC for minimal CT-FFR was 0.597 (proximal) vs. 0.567 (distal) and for ∆CT-FFR the AUC was 0.584 (proximal) vs. 0.515 (distal). Regarding revascularization the AUC for minimal CT-FFR was 0.843 (proximal) vs. 0.847 (distal) and for maximal ∆CT-FFR the AUC was 0.846 (proximal) vs. 0.737 (distal). Conclusion CT-derived FFR has modest predictive value for future cardiovascular events. Distal measurements are not superior to measurements limited to proximal coronary segments.