Use of physioLogy to evaluaTe procedural Result After percutaneous coronary intervention of Chronic Total Occlusion (ULTRA-CTO): protocol for a prospective, single-arm, multicentre, exploratory study.

introductionPost-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) is associated with future major adverse cardiac events and may reflect residual ischaemia and suboptimal stent result (SSR). Post-PCI FFR should therefore be considered to identify patients at high risk. Whether abnormal post-PCI FFR and non-hyperaemic pressure ratios, including resting full-cycle ratio (RFR), represent SSR after PCI remains to be determined, especially after chronic total occlusion (CTO) PCI. In addition, little is known about the association between post-PCI intracoronary physiology and SSR with residual anginal complaints. METHODS AND ANALYSIS: The physioLogy to evaluaTe procedural Result After percutaneous coronary intervention of Chronic Total Occlusion study is a prospective, multicentre, exploratory, mechanistic, investigator-initiated, single-arm study with a non-inferiority design. A total of 200 patients, undergoing CTO PCI, with FFR and RFR measured in all patients, will be included at two study sites in the Netherlands. The primary endpoint is the area under the curve (AUC) of post-PCI RFR, in comparison to the AUC of post-PCI FFR, for prediction of optical coherence tomography-detected SSR and its individual components. ETHICS AND DISSEMINATION: The study is approved by the local ethical review board ('Medisch Ethische Toetsing Commissie Isala Zwolle'). Written informed consent will be obtained from all patients before enrolment. The outcomes of this study are intended to be disseminated in a peer-reviewed journal. STUDY REGISTRATION: NCT04780971.