Quantitative Flow Ratio for Evaluating Coronary Artery Disease in Patients With Aortic Stenosis Undergoing Transcatheter Aortic Valve Implantation

Patients with severe aortic stenosis (AS) frequently present with concomitant coronary artery disease (CAD), which poses challenges in clinical management and procedural planning. The diagnostic reliability of conventional physiological indices such as fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) may be compromised by the altered hemodynamics associated with AS. This has prompted interest in alternative assessment modalities. Quantitative Flow Ratio (QFR), an angiography-based, wire-free index, has emerged as a promising tool for functional lesion assessment. However, its validity and clinical utility in the setting of transcatheter aortic valve implantation (TAVI) are still under evaluation. This systematic review synthesizes evidence from eleven key studies (eight primary studies and three secondary analyses/substudies), evaluating the diagnostic performance and prognostic relevance of QFR in patients with severe AS. Overall, QFR pre-TAVI showed a strong correlation with FFR across multiple studies, with area under the curve often exceeding 0.90. The diagnostic agreement between QFR and FFR was higher than that observed between FFR and non-hyperemic indices. However, up to 30% of vessels were excluded due to suboptimal image quality, underscoring the need for standardized angiographic acquisition protocols. Importantly, QFR accuracy appeared to decline with increasing AS severity, particularly in patients with an aortic valve area of < 0.60 cm 2 . Preliminary prognostic data indicate that QFR-defined lesion severity may predict mortality in TAVI patients. Overall, while QFR shows good reliability, larger prospective studies are needed to validate its role in clinical decision-making and risk stratification in this high-risk population.