Agreement of the Resting Distal to Aortic Coronary Pressure With the Instantaneous Wave-Free Ratio.

Background: Recently, 2 randomized controlled trials showed that the instantaneous wave-free ratio (iFR), a resting coronary physiological index, is noninferior to fractional flow reserve for guiding revascularization. The resting distal to aortic coronary pressure (P/P) measured at rest is another adenosine-free index widely available in the cardiac catheterization laboratory; however, little is known about the agreement of P/P using iFR as a reference standard.

Objectives: The goal of this study was to investigate the agreement of P/P with iFR.

Methods: A total of 763 patients were prospectively enrolled from 12 institutions. iFR and P/P were measured under resting conditions. Using iFR ≤0.89 as a reference standard, the agreement of P/P and its best cutoff value were assessed.

Results: According to the independent core laboratory analysis, iFR and P/P were analyzable in 627 and 733 patients (82.2% vs. 96.1%; p < 0.001), respectively. The median iFR and P/P were 0.90 (interquartile range: 0.85 to 0.94) and 0.92 (interquartile range: 0.88 to 0.95), and the 2 indices were highly correlated (R = 0.93; p < 0.001; iFR = 1.31 * P/P -0.31). According to the receiver-operating characteristic curve analysis, P/P showed excellent agreement (area under the curve: 0.98; 95% confidence interval: 0.97 to 0.99; p < 0.001) with a best cutoff value of P/P ≤0.91. The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 93.0%, 91.4%, 94.4%, 93.3%, and 92.7%, respectively. These results were similar in patients with acute coronary syndrome and stable angina.

Conclusions: P/P was analyzable in a significantly higher number of patients than iFR. P/P showed excellent agreement with iFR, suggesting that it could be applied clinically in a similar fashion. (Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology? [CONTRAST]; NCT02184117).