Hyperemic versus non-hyperemic indexes for coronary physiology assessment in patients with severe aortic stenosis.

PURPOSE: Recent data suggests that fractional flow reserve (FFR) may underestimate intermediate coronary stenosis in the presence of severe aortic stenosis (AS), whereas instantaneous wave-free ratio (iFR) values may remain similar after treatment of AS, yet the evidence still lacks to use iFR as the reference. We aimed to compare FFR/iFR values in the AS setting. MATERIALS AND METHODS: The functional significance of 416 coronary lesions in 221 patients with severe AS was investigated with iFR and FFR. RESULTS: The diagnostic agreement between iFR and FFR has been tested, using the cut-off value of 0.89 for iFR and 0.80 for FFR. The mean diameter stenosis was 58.6 â€‹± â€‹13.4% with FFR of 0.85 â€‹± â€‹0.07 and iFR of 0.90 â€‹± â€‹0.04. FFR ≤0.80 was identified in 26.0% and iFR≤0.89 in 33.2% of interrogated vessels. Good agreement between iFR and FFR was confirmed (Intraclass Correlation Coefficient 0.83 [95%CI 0.79-0.85]). The overall diagnostic accuracy (AUC in ROC analysis) of FFR in detecting iFR≤0.89 was 0.997 (95%CI 0.986 to 1.000; p<0.001) and of iFR in detecting FFR≤0.80 was 0.995 (95%CI 0.983 to 0.999; p<0.001). The optimal cut-off value for FFR to detect iFR≤0.89 was 0.82 with sensitivity, specificity, and accuracy of 97.1%, 98.9%, and 97.7%, respectively, and for IFR to detect FFR≤0.80 was 0.88 with sensitivity, specificity, and accuracy of 99.1%, 95.8%, and 97.4%, respectively. CONCLUSION: In the presence of AS, FFR has good agreement with iFR. However, the optimal FFR/iFR threshold to identify iFR≤0.89/FFR≤0.80 may be different from the standard thresholds of ischemia.