Diagnostic accuracy of Murray law-based quantitative flow ratio in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

Murray law-based quantitative flow ratio (μQFR) is a novel computational method that enables accurate estimation of fractional flow reserve (FFR) using a single angiographic projection. However, its diagnostic value in patients with severe aortic stenosis (AS) remains unclear.

We included 25 consecutive patients who underwent transcatheter aortic valve replacement (TAVR) for severe AS with intermediate or greater (30–90%) coronary artery disease (CAD). Pre- and post-TAVR μQFR, QFR, instantaneous flow reserve (iFR), and post-TAVR invasive FFR values were measured. We evaluated the diagnostic performance of pre-TAVR μQFR, QFR, and iFR using post-TAVR FFR ≤ 0.80 as a reference standard of ischemia.

Pre-TAVR μQFR was significantly correlated with post-TAVR FFR (r = 0.73, p < 0.0001). The area under the curve of pre-TAVR μQFR on post-TAVR FFR ≤ 0.8 was 0.91 (95% confidence interval [CI] 0.77–0.98), comparable to that of pre-TAVR iFR (0.86 [95% CI 0.71–0.98], p = 0.97). The accuracy, sensitivity, specificity, and positive and negative predictive values of pre-TAVR μQFR on post-TAVR FFR ≤ 0.8 were 84.2% (95% CI 68.7–93.4), 61.6% (95% CI 31.6–86.1), 96.0% (95% CI 79.6–99.9), 88.9% (95% CI 52.9–98.3), and 82.8% (95% CI 70.6–90.6), respectively. For pre-TAVR iFR, these values were 76.5% (95% CI 58.8–89.3), 90.9% (95% CI 58.7–99.8), 69.6% (95% CI 47.1–86.8), 58.8% (95% CI 42.8–73.1), and 94.1% (95% CI 70.8–99.1), respectively.

μQFR could be useful for the physiological evaluation of patients with severe AS with concomitant CAD.