Fractional Flow Reserve and Instantaneous Wave-Free Ratio as Predictors of the Placebo-Controlled Response to Percutaneous Coronary Intervention in Stable Coronary Artery Disease

Background: The Placebo-controlled Trial of Percutaneous Coronary Intervention for the Relief of Stable Angina (ORBITA-2) provided evidence for the role of percutaneous coronary intervention (PCI) for angina relief in stable coronary artery disease (CAD). Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are often used to guide PCI, however their ability to predict placebo-controlled angina improvement is unknown. Methods: Participants with angina, ischemia, and stable CAD were enrolled and antianginal medications were stopped. Participants reported angina episodes daily for 2 weeks using the ORBITA-app. At the research angiogram, FFR and iFR were measured. After sedation and auditory isolation, participants were randomized to PCI or placebo, before entering a 12-week blinded follow-up phase with daily angina reporting. The ability of FFR and iFR, analyzed as continuous variables, to predict the placebo-controlled effect of PCI, was tested using Bayesian proportional odds modelling. Results: Invasive physiology data were available in 279 patients (140 PCI and 139 placebo). The median (IQR) age was 65 years (59.0 to 70.5) and 223 (79.9%) were male. Median FFR was 0.60 (0.46 to 0.73) and median iFR was 0.76 (0.50 to 0.86). The lower the FFR or iFR, the greater the placebo-controlled improvement with PCI across all endpoints. There was strong evidence that a patient with an FFR at the lower quartile would have a greater placebo-controlled improvement in angina symptom score with PCI than a patient at the upper quartile (FFR 0.46 vs. 0.73: OR 2.01, 95% CrI 1.79 to 2.26, Pr(Interaction)>99.9%). Similarly, there was strong evidence that a patient with an iFR at the lower quartile would have a greater placebo controlled improvement in angina symptom score with PCI than a patient with an iFR at the upper quartile (iFR 0.50 vs. 0.86: OR 2.13, 95% CrI 1.87 to 2.45, Pr(Interaction) >99.9%). The relationship between benefit and physiology was seen in both Rose angina and Rose nonangina. Conclusions: Physiological stenosis severity, as measured by FFR and iFR, predicts placebo-controlled angina relief from PCI. Invasive coronary physiology can be used to target PCI to those patients who are most likely to experience benefit.