A Comparison between the Instantaneous Wave-free Ratio and Resting Distal Coronary Artery Pressure/Aortic Pressure and the Fractional Flow Reserve: The Diagnostic Accuracy Can Be Improved by the Use of both Indices

Objectives The fractional flow reserve (FFR) is an index of the severity of coronary stenosis that has been clinically validated in several studies. The instantaneous wave-free ratio (iFR) and the resting distal coronary artery pressure/aortic pressure (Pd/Pa) are nonhyperemic pressure-derived indices of the severity of stenosis. This study sought to examine the diagnostic accuracy of the iFR and resting Pd/Pa with respect to hyperemic FFR. Methods Following an intracoronary injection of papaverine, the iFR, resting Pd/Pa, and FFR were continuously measured in 123 lesions in 103 patients with stable coronary disease. Results The iFR and resting Pd/Pa values were strongly correlated with the FFR (R=0.794, p<0.001, R=0.832, p<0.0001, respectively). A receiver operator curve (ROC) analysis revealed that the optimal iFR cut-off value for predicting an FFR of <0.80 was 0.89 (AUC 0.901, sensitivity 84.1%, specificity 80.0%, positive predictive value 69.8%, negative predictive value 90.0%, diagnostic accuracy 81.3%), while the optimal resting Pd/Pa cut-off value was 0.92 (AUC 0.925, sensitivity 90.9%, specificity 78.5%, positive predictive value 70.2%, negative predictive value 93.9%, diagnostic accuracy 82.9%). The lesions with an iFR value of ≤0.89 and a Pd/Pa value of ≤0.92 were defined as double-positive lesions, while the lesions with an iFR value of >0.89 and a Pd/Pa value of >0.92 were defined as double-negative lesions. In these 109 lesions, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 92.3%, 82.9%, 75.0%, 95.1%, and 86.2%, respectively. Conclusion This analysis demonstrated that the iFR and resting Pd/Pa were strongly correlated with the FFR and that the diagnostic accuracy of the iFR was similar to that of the resting Pd/Pa. The diagnostic accuracy can be improved with the use of both the iFR and the resting Pd/Pa.