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"

Abstract

Background: 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. Design/Methods: 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 (CFRp-3D). Conclusion: 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. Clinical Trial Registration: ClinicalTrials.gov (NCT04857762).

Keywords: coronary artery disease; coronary flow reserve (CFR); fractional flow reserve (FFR); microvascular coronary disease; resting full-cycle ratio (RFR).

Conflict of interest statement

The patent of the method detailed in the extended physiology sub-study has been issued by the European Patent Office (WO2019175612, applicant: University of Debrecen).

Copyright © 2021 Kőszegi, Berta, Tóth, Tar, Üveges, Ágoston, Szücs, Szabó, Barta, Szük, Czuriga, Komócsi and Ruzsa.

Figures

Figure 1

Definition of the investigated coronary segments and the corresponding left ventricular segments on the polar map.

Figure 2

RFR pullback investigation in the left circumflex artery with intermediate stenoses. Both lesions proved to be significant according to the local ΔRFR.

Figure 3

Flow chart of the comparison of the visual assessment and the results of the RFR measurement.

Figure 4

Summary of methods used in the extended physiology sub-study. RFR, resting full cycle ratio; FFR, fractional flow reserve; CFR, coronary flow reserve; MRR, microvascular resistance reserve; f, viscous friction losses; s, separation losses; Q, volumetric flow; ΔP, pressure gradient between the proximal and distal coronary pressure; Pd, distal coronary pressure.

Figure 5

Flow-chart of the proposed clinical decision-making process according to the results of physiological measurements.