The inter-study reproducibility of instantaneous wave-free ratio and angiography coregistration.

BACKGROUND: Coregistration system of instantaneous wave-free ratio (iFR) pullback and angiography has been developed to enhance benefits of physiology oriented percutaneous coronary intervention (PCI), but its reproducibility has not yet been fully assessed. METHODS AND RESULTS: In 51 coronary arteries from 39 patients with stable coronary artery disease, iFR angio-coregistrations were repeated twice. The mean iFR values were comparable between the first and second studies (0.85 ±â€¯0.12 vs. 0.84 ±â€¯0.13, p = 0.97). In terms of a coronary segment with predominant iFR gradients defined by the largest segmental iFR gradients, the repeated iFR angio-coregistrations matched in 47 of 51 (92%) studies and showed good agreement (κ = 0.75) in overall vessels. When assessed only in vessels with positive iFR (≤0.89), iFR angio-coregistrations matched in 31 of 32 (97%) studies and showed an excellent agreement (κ = 0.91). The predominant iFR gradients in the repeated iFR angio-coregistrations demonstrated strong correlation (r = 0.96, p < 0.0001) and an excellent agreement: mean difference was 0.0006, and the lower and upper limits (mean difference ±â€¯1.96 standard deviation) of agreement were -0.0312 and 0.0324. CONCLUSIONS: iFR angio-coregistration is highly reproducible and can precisely identify a suitable target for PCI.