Diagnostic Accuracy of Artificial Intelligence–Enhanced Ultrasonic Flow Ratio for On-Site Assessment of Coronary Stenosis

BACKGROUND: Ultrasonic flow ratio (UFR) is an artificial intelligence-powered method that derives fractional flow reserve (FFR) from intravascular ultrasound (IVUS) imaging. Although retrospective core laboratory studies have demonstrated its diagnostic accuracy, prospective on-site validation remains unexplored. OBJECTIVES: The aim of this study was to evaluate the diagnostic accuracy of on-site UFR for identifying hemodynamically significant coronary stenosis, using wire-based FFR as the reference standard. METHODS: Consecutive patients with ≥1 de novo lesion exhibiting 50% to 80% diameter stenosis and reference diameter ≥2.5 mm were prospectively enrolled. After FFR measurement, IVUS pull backs were acquired and analyzed on site using dedicated software, with analysts blinded to FFR results. Minimal luminal area (MLA) was simultaneously available during UFR computation. The prespecified primary endpoint was the on-site diagnostic accuracy of UFR for identifying FFR ≤0.80. RESULTS: Between February 2023 and November 2024, 112 patients (138 pull backs) were enrolled; after the exclusion of 6 patients (7 pull backs), 106 patients with 131 vessels remained for analysis. Median FFR was 0.84 (Q1-Q3: 0.78-0.90), with 43 of 131 lesions (32.8%) showing FFR ≤0.80. UFR achieved diagnostic accuracy of 94% (95% CI: 88%-97%), significantly exceeding the prespecified target of 78% (P < 0.001). Compared with IVUS-derived MLA, UFR demonstrated superior sensitivity (88% [95% CI: 75%-96%] vs 47% [95% CI: 31%-62%]; P < 0.001) and specificity (97% [95% CI: 90%-99%] vs 84% [95% CI: 75%-91%]; P = 0.003). The corresponding positive and negative predictive values were 93% (95% CI: 81%-97%) and 94% (95% CI: 88%-97%), respectively. CONCLUSIONS: This study achieved its prespecified primary goal by demonstrating high on-site diagnostic accuracy of UFR in identifying hemodynamically significant coronary stenosis. (Functional Comprehensive Assessment by IVUS Reconstruction in Patients With Suspected Ischemic Heart Disease [FEATURE]; NCT05694065).