Diagnostic Accuracy of Angiography‐Derived Murray Law‐Based Quantitative Flow Ratio (μQFR) Versus Pressure‐Derived Fractional Flow Reserve (FFR) in Moderate to Severe Calcified Coronary Lesions—The DIAMOND Study

Background Murray law‐based Quantitative Flow Ratio (μQFR) is an innovative AI‐driven method for evaluating coronary lesions using contrast flow velocity estimates. Unlike traditional approaches, μQFR does not require pressure wires or hyperemia induction. However, its accuracy compared to Fractional Flow Reserve (FFR) for calcified lesions (ACC/AHA classification B2 or C) remains underexplored. Aims This study aimed to evaluate the diagnostic accuracy of μQFR in detecting hemodynamically significant calcified coronary stenosis, defined as FFR ≤ 0.80. Methods In this two‐center, investigator‐initiated trial, patients with calcified lesions (B2 or C, 30%–90% diameter stenosis) and FFR assessment during coronary angiography were included. μQFR was calculated by a nurse blinded to the FFR results. Sensitivity and specificity of μQFR were compared with FFR as the gold standard. Results Among 125 patients, paired μQFR and FFR data were available for 107 patients and 120 lesions. Mean FFR, μQFR, and percent stenosis were 0.775 (95% CI: 0.757–0.793), 0.788 (95% CI: 0.772–0.805), and 56.75% ( ± 10.14%), respectively. μQFR demonstrated a sensitivity of 75% (95% CI: 65.6%–84.6%), a specificity of 77.8% (95% CI: 63.5%–92.0%), a diagnostic precision of 75.8% and an area under the receiver operating characteristic curve of 0.813 (95% CI: 0.714–0.911). The positive predictive value was 88.7%, and the negative predictive value was 57.1%. The positive and negative likelihood ratios were 3.38 and 0.32, respectively. Conclusion μQFR is simple to compute and offers moderate diagnostic accuracy for calcified coronary stenosis. It provides a valuable alternative when FFR is unavailable or technically challenging.