Effects of successful percutaneous coronary intervention of chronic total occlusions with demonstrable viability or ischemia: A protocol for a systematic review

Background Chronic coronary total occlusion (CTO) is a common finding in patients referred to coronary angiography. To sustain blood flow distally to the occlusion site, collateral circulation is formed from preexisting vessels. While these collaterals may partial or completely preserve perfusion at rest, they may be insufficient when increased blood flow is needed. According to current guidelines, percutaneous coronary intervention (PCI) is recommended solely in patients with resistant angina despite optimal medical therapy or when a large area of documented ischemia in the territory of the occluded vessel is present. Randomised controlled trials (RCTs) suggest its benefit in the improvement of patients’ quality of life and symptoms, despite their conflicting results concerning prognosis and left ventricular function. However, most of these studies often lack data regarding myocardial ischemic burden and viability, assessed by imaging methods. Therefore, the purpose of the systematic review is to comprise and analyse the literature on whether viability or ischemia-guided PCI of CTO, identified by imaging methods, has an impact on the clinical outcomes of the patients. Methods We will conduct a thorough research in different databases, including PubMed/MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection, Clinical trials in the European Union, and ClinicalTrials.gov . We will include RCTs, cohort studies, cross-sectional studies, and case-control studies, in which patients with established CTO were tested for viability and/or ischemia before the decision to perform PCI and were evaluated by post-intervention testing or clinical endpoint follow-up. Two authors will independently review the selected studies, and any discrepancies will be solved by a third element. Subsequently, data from the various eligible studies will be extracted and analysed by two different authors. No subgroup analysis is planned. Ethics and disclosure Ethical approval will not be required for this study as it is an analysis of previously published articles (i.e., secondary data). The results will be published in a peer-reviewed journal. PROSPERO registration CRD42023426858.