Comparison of Flow Ratio Derived From IVUS With CAG in Complex Lesions: Correlation With FFR

Accurate evaluation of coronary artery disease is critical for guiding treatment decisions, particularly in complex coronary lesions. Fractional flow reserve (FFR) remains the gold standard for assessing lesion-specific ischemia but is invasive and requires pharmacological hyperemia. Noninvasive alternatives, such as quantitative flow ratio (QFR) from coronary angiography and ultrasonic flow ratio (UFR) from intravascular ultrasound (IVUS), offer promising diagnostic approaches.

This study aimed to compare the diagnostic performance of UFR and QFR against FFR in assessing complex coronary lesions.

This retrospective multicenter study included 217 patients (220 vessels) who underwent IVUS and FFR. UFR was derived from IVUS imaging, and QFR was calculated using coronary angiography data. Correlation, agreement, and diagnostic metrics (sensitivity, specificity) were analyzed, with receiver operating characteristic curves assessing accuracy.

UFR demonstrated stronger correlation with FFR (r = 0.79; 95% CI: 0.74-0.84; P < 0.001) compared with QFR (r = 0.68; 95% CI: 0.60-0.74; P < 0.001). UFR also showed better diagnostic performance, with an area under the receiver operating characteristic curve of 0.91 (95% CI: 0.86-0.94) compared with QFR's 0.86 (95% CI: 0.81-0.90). In complex lesions (diffuse, bifurcation, calcified), UFR consistently outperformed QFR, particularly in bifurcation and lesions heavily calcified, where QFR accuracy dropped significantly (72.5% vs 86.8%, P = 0.001).

In this retrospective hypothesis-generating study, UFR showed numerically higher diagnostic accuracy than QFR in complex coronary lesions. These findings suggest UFR may have potential as a complementary tool for functional assessment, but definitive conclusions about superiority require validation in larger prospective studies. (Comparison of UFR With QFR in Stable Coronary Artery Disease; NCT06322355).