Sex Differences in Murray Law-Based Quantitative Flow Ratio Among Patients With Intermediate Coronary Lesions

Background The Murray law-based quantitative flow ratio (μQFR) is a novel technique that simulates fractional flow reserve (FFR) from a single angiographic view. However, the impact of sex differences on the diagnostic performance of μQFR has not been investigated. Methods and Results In this study, FFR and μQFR were assessed in 497 intermediate stenoses (30%-70% by visual estimation) from 460 patients (34.3% female). Physiological significance was defined as FFR ≤0.80 or μQFR ≤0.80. After adjusting for potential confounders, female sex was independently associated with higher FFR (P=0.048 and 0.026, respectively) and μQFR (P=0.001 for both) in both fully adjusted and stepwise backward models. μQFR provided superior diagnostic accuracy compared with angiography alone for detecting FFR ≤0.80 in both women (area under the curve, 0.93 [95% CI, 0.88-0.97] versus 0.80 [95% CI, 0.73-0.86]; P=0.001) and men (area under the curve, 0.88 [95% CI, 0.84-0.92] versus 0.73 [95% CI, 0.68-0.78]; P<0.001), with comparable performance between the sexes (P=0.175). In the multivariable analysis, sex was not a significant factor contributing to the overall disagreement between FFR and μQFR. Conclusions Regardless of angiographic stenosis severity, women tend to have higher FFR and μQFR values than men. Furthermore, μQFR performs similarly well in both sexes and offers improved diagnostic accuracy over angiography alone, indicating its potential as a reliable, wire-free tool to identify functional ischemia.