Abstract

Aims: The instantaneous wave-free ratio (iFR) and whole-cycle Pd/Pa investigate coronary physiology during non-hyperaemic conditions. To test for unique physiologic properties of the wave-free period when making resting coronary pressure measurements, we compared post hoc a diastolic pressure ratio (dPR) and Pd/Pa against iFR for numerical similarity and test/retest repeatability. Methods and results: Eight hundred and ninety-three lesions from 833 subjects were included from the VERIFY 2 and CONTRAST studies. Diastolic pressure ratio and a linear transform of Pd/Pa were compared against iFR for diagnostic performance. Mean difference between dPR and iFR [Δ = −0.006 ± 0.011, r2 = 0.993, area under receiver operating characteristic (ROC) curve (AUC) = 0.997] mirrored the difference of two iFR measurements repeated immediately (Δ = <0.001 ± 0.004, r2 = 0.998, AUC = 1.00). Minor variations in the definition of dPR changed its value by <1–2% over a broad range of the cardiac cycle. A linear transform of Pd/Pa showed very good diagnostic performance (Δ = −0.012 ± 0.031, r2 = 0.927, AUC = 0.979). Post hoc iFR values were validated against real-time iFR values and matched almost exactly (average Δ = <0.001 ± 0.004, 99.6% within ±0.01). Conclusions: Our dPR offers numerical equivalency to iFR. Despite different technical approaches for identifying the relevant period of diastole, the agreement between dPR and iFR and the insensitivity of dPR to minor variations in its definition further confirm numerical equivalency among resting metrics.