OUFR Versus FFR for Functional Assessment of Coronary Artery Stenosis in Patients With Unstable Angina

Hybrid intravascular ultrasound-optical coherence tomography (IVUS-OCT) imaging can integrate both advantages. Optical ultrasonic flow ratio (OUFR) was recently developed for functional assessment. This study aimed to verify the diagnostic performance of OUFR using fractional flow reserve (FFR) as the reference standard. From February 2023 to June 2023, 80 patients (126 vessels) with unstable angina pectoris were assessed with FFR and either hybrid IVUS-OCT or stand-alone IVUS imaging before percutaneous coronary intervention in a prospective series. OUFR based on OCT alone (OUFRO) or based on both (OUFROI) were derived from hybrid IVUS-OCT imaging in 61 patients (86 vessels). OUFR based on IVUS alone (OUFRI) was derived from single modality IVUS imaging in 58 patients (80 vessels). In all cases, wire-based FFR was measured in the same vessels for comparison. All 3 computed OUFR indexes achieved high agreement with FFR, with OUFROI and OUFRO showing higher correlation with FFR (r = 0.88; P < 0.001; r = 0.85; P < 0.001, respectively) than OUFRI (r = 0.73; P < 0.001). Compared with OUFRO, the integration of both IVUS and OCT (OUFROI) further improved the diagnostic accuracy for predicting FFR ≤0.80 with accuracy, sensitivity, and specificity being 95%, 94%, and 96%, respectively. The area under the curve of OUFROI to predict FFR ≤0.80 was 0.99, higher than that for OUFRO (0.95) and OUFRI (0.91). OUFROI is feasible and accurate in the prospective study, resulting in excellent agreement with FFR, superior to single imaging modality-based physiology indexes.