Anatomical Assessment vs. Pullback REsting full-cycle rAtio (RFR) Measurement for Evaluation of Focal and Diffuse CoronarY Disease: Rationale and Design of the "READY Register".

The morphology and functional severity of coronary stenosis show poor correlation. However, in clinical practice, the visual assessment of the invasive coronary angiography is still the most common means for evaluating coronary disease. The fractional flow reserve (FFR), the coronary flow reserve (CFR), and the resting full-cycle ratio (RFR) are established indices to determine the hemodynamic significance of a coronary stenosis. The READY register (NCT04857762) is a prospective, multicentre register of patients who underwent invasive intracoronary FFR and RFR measurement. The main aim of the registry is to compare the visual estimate of coronary lesions and the functional severity of the stenosis assessed by FFR, as well as the RFR pullback. Characterizations of the coronary vessel for predominantly focal, diffuse, or mixed type disease according to visual vs. RFR pullback determination will be compared. The secondary endpoint of the study is a composite of major adverse cardiac events, including death, myocardial infarction, and repeat coronary revascularization at 1 year. These endpoints will be compared in patients with non-ischemic FFR in the subgroup of cases where the local pressure drop indicates a focal lesion according to the definition of ΔRFR > 0.05 (for <25 mm segment length) and in the subgroup without significant ΔRFR. In case of an FFR value above 0.80, an extended physiological analysis is planned to diagnose or exclude microvascular disease using the CFR/FFR index. This includes novel flow dynamic modeling for CFR calculation (CFR). The READY register will define the effect of RFR measurement on visual estimation-based clinical decision-making. It can identify a prognostic value of ΔRFR during RFR pullback, and it would also explore the frequency of microvascular disease in the patient population with FFR > 0.80. ClinicalTrials.gov (NCT04857762).