Correlation between intracoronary physiology and myocardial perfusion imaging in patients with severe aortic stenosis

Background: Aortic stenosis (AS) is frequently associated with coronary artery disease (CAD). However, the best tool to functionally assess CAD in AS remains undetermined. Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) have never been validated in AS. Methods: FFR, iFR and stress single photon emission computed tomography (SPECT) were performed in a consecutive series of 28 patients with severe AS and 41 borderline coronary lesions during the work-up for valve replacement. Results: Both FFR and iFR were correlated with an abnormal SPECT. At ROC analysis, FFR yielded an AUC = 0.91 with negative predictive value (NPV) = 95% in detecting ischemia according to SPECT. iFR showed significant worse agreement with myocardial perfusion imaging compared to FFR (59% vs 85%, p = 0.014). Specifically, a significant larger proportion of false positive measurements (negative SPECT and iFR < 0.89) was observed using iFR vs FFR: 39% vs 12%, p = 0.011. Using a pre-specified 0.82 cut-off, the iFR agreement with SPECT increased to 73%. Conclusions: FFR yielded a good correlation with SPECT and a high NPV in detecting ischemia-provoking lesions. iFR diagnostic metrics were inferior compared with FFR and improved adopting a lower ischemic threshold.