Coronary physiology in patients with severe aortic stenosis: Comparison between fractional flow reserve and instantaneous wave-free ratio

The functional assessment of coronary artery disease (CAD) in patients with aortic stenosis (AS) has not been validated so far, and the best strategy to physiologically investigate the relevance of coronary stenosis in this specific setting of patients remains undetermined. The aim of the study is to compare the diagnostic performance of instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) in patients with severe AS.The functional significance of 179 coronary lesions was investigated with on-line iFR and FFR measurements in 85 AS patients and compared with a control group formed by 167 patients (290 lesions) with stable CAD and without AS. The iFR-FFR diagnostic agreement has been tested using the conventional 0.80 FFR cut-off.The correlation between iFR and FFR was similar between AS and CAD patients, as well as the area under the curve at ROC curve analysis (0.97 vs 0.96, p=0.88). However, using the standard iFR 0.89 threshold, the diagnostic accuracy of iFR was significantly lower in AS compared with CAD (76.3% vs 86.1%, p=0.009). According to ROC analysis, the best iFR cut-off in predicting FFR≤0.8 was lower in AS (0.83, J=0.82) compared with CAD (0.89, J=0.81). Using the ROC derived cut-off of 0.83, the iFR accuracy increased significantly (91.3%, p=0.003) while maintaining an elevated negative predictive value (95.5%).In the presence of severe AS, conventional iFR cut-off had lower diagnostic agreement with FFR classification of coronary lesions compared to stable CAD patients. AS seems to influence iFR cut-off ischemic thresholds and deserves further comparative studies.