Diagnostic Performance of Resting and Hyperemic Invasive Physiologic Indices to Define Myocardial Ischemia: Validation with 13N-Ammonia Positron Emission Tomography

Abstract

Introductions: Diagnostic performance of invasive physiologic indices was reported to be different according to the reference to define the presence of myocardial ischemia. Therefore, we sought to compare the diagnostic performance of fractional flow reserve (FFR), instantaneous wave-free ratio (iFR) and resting distal coronary artery pressure/aortic pressure (Pd/Pa) using 13N-ammonia positron emission tomography (PET).

Methods: A total of 115 consecutive patients with left anterior descending artery stenosis who underwent both 13N-ammonia PET and invasive physiologic measurement were included. Optimal cutoff values and diagnostic performance of FFR, iFR and resting Pd/Pa were assessed using PET-derived coronary flow reserve (CFR) and relative flow reserve (RFR) as a reference. To compare discrimination and reclassification ability, each index was compared with integrated discrimination improvement (IDI) and category-free net reclassification index (NRI).

Results: All invasive physiologic indices correlated with CFR and RFR (all p values<0.001). The overall diagnostic accuracies of FFR, iFR and resting Pd/Pa were not different for CFR<2.0 (FFR 69.6%, iFR 73.9% and resting Pd/Pa 70.4%) and RFR<0.75 (FFR 73.9%, iFR 71.3% and resting Pd/Pa 74.8%). Discrimination and reclassification abilities of invasive physiologic indices were comparable for CFR. For RFR, FFR showed better discrimination and reclassification ability than resting indices (relative IDI=1.332 and category-free NRI=0.971 for iFR

relative IDI=1.592 and category-free NRI=1.058 for resting Pd/Pa

all p values<0.001).

Conclusions: The diagnostic performance of invasive physiologic indices showed no differences in the prediction of myocardial ischemia defined by CFR. Using RFR as a reference, FFR showed a better discrimination and reclassification ability than resting indices.