Murray law-based quantitative flow ratio for functional assessment of coronary lesions: a systematic review and...

Angiography-derived coronary physiology has emerged as an attractive alternative to pressure-wire-based fractional flow reserve (FFR) for functional lesion assessment. Murray law-based quantitative flow ratio (µQFR) represents a simplified, single-view approach, but its diagnostic performance across diverse clinical settings remains incompletely defined. To evaluate the diagnostic accuracy of µQFR for identifying functionally significant coronary lesions using invasive FFR as the reference standard. We performed a systematic review and diagnostic accuracy meta-analysis in accordance with PRISMA-DTA recommendations. Studies assessing µQFR against invasive FFR (≤ 0.80) with extractable lesion-level data were included. Sensitivity and specificity were pooled using a bivariate random-effects model. Secondary analyses explored performance in patients undergoing transcatheter aortic valve implantation (TAVI) and in calcified coronary lesions. Seven studies comprising 1,826 coronary lesions were included. µQFR demonstrated a pooled sensitivity of 0.807 (95% CI 0.690-0.888) and specificity of 0.944 (95% CI 0.893-0.971), with a positive likelihood ratio of 14.41, negative likelihood ratio of 0.20, and diagnostic odds ratio of 70.6. Specificity remained consistently high, whereas sensitivity showed substantial variability. In exploratory subgroup analyses, sensitivity was 0.77 (95% CI 0.64-0.87) in TAVI patients (2 studies; 236 lesions) and 0.72 (95% CI 0.66-0.78) in calcified lesions (2 studies; 691 lesions); these findings are hypothesis-generating only. µQFR demonstrates promising diagnostic accuracy with consistently high specificity. However, its moderate sensitivity, negative likelihood ratio of 0.20, and reduced performance in calcified lesions limit its ability to safely exclude functionally significant disease. Prospective validation is required before µQFR can be recommended as a standalone decision-making tool.