Turkish Chronic Total Occlusion Percutaneous Coronary Intervention Registry

The TURK CTO Registry is a prospective, multicenter, observational registry designed to provide comprehensive, real-world data on contemporary percutaneous coronary intervention (PCI) for coronary chronic total occlusion (CTO) across participating centers in Türkiye. The registry is planned to continue for 10 years and will prospectively enroll consecutive eligible patients undergoing CTO PCI.

The registry will evaluate patient-, lesion-, procedure-, operator-, and center-related characteristics and their associations with procedural strategies, technical and procedural success, complications, and short- and long-term clinical outcomes.

A coronary CTO will be defined as a coronary artery lesion with Thrombolysis in Myocardial Infarction (TIMI) grade 0 antegrade flow and an estimated duration of occlusion of at least 3 months, based on clinical history, previous angiographic findings, or other available clinical information.

Eligibility Criteria Inclusion Criteria

Participants will be eligible for inclusion in the TURK CTO Registry if they meet all of the following criteria:

Age ≥18 years. Presence of at least one coronary chronic total occlusion (CTO), defined as a coronary artery lesion with TIMI grade 0 antegrade flow and an estimated duration of occlusion of at least 3 months based on clinical history, previous angiographic findings, or other available clinical information.

Undergoing an attempted percutaneous coronary intervention (PCI) of the CTO at a participating center during the study period.

Provision of written informed consent for participation in the registry, where required by the applicable ethics committee and local regulations.

Both successful and unsuccessful CTO PCI procedures will be included.

Patients undergoing repeat CTO PCI attempts after a previous unsuccessful or incomplete CTO PCI procedure will also be included in the registry. Each CTO PCI attempt will be recorded as a separate procedural episode and linked to the same patient using a unique study identifier. This will allow assessment of repeat procedures, changes in crossing strategy and devices, reasons for previous failure, subsequent procedural success, complications, and clinical outcomes.

If a patient undergoes PCI for more than one CTO lesion, each eligible CTO PCI procedure will be recorded separately and linked to the same patient, allowing both patient-level and procedure-level analyses.

Exclusion Criteria

Participants will be excluded if any of the following criteria are present:

Age <18 years. Coronary lesions that do not meet the predefined criteria for a chronic total occlusion.

No CTO PCI attempt performed during the index procedure. Inability or refusal to provide informed consent when informed consent is required for study participation.

Withdrawal of consent for participation in the registry.

Patients will not be excluded on the basis of CTO lesion complexity, previous failed CTO PCI attempts, previous PCI, previous coronary artery bypass graft surgery, comorbidities, or the CTO crossing strategy, technique, guidewire, microcatheter, device, or adjunctive technology selected by the treating operator.

Patient and Clinical Characteristics

Baseline data will include demographic characteristics, cardiovascular risk factors, comorbidities, previous cardiovascular events and coronary revascularization procedures, clinical presentation, cardiac function, relevant laboratory and clinical parameters, and current cardiovascular treatment. Previous attempts at CTO revascularization and other factors potentially influencing procedural complexity and clinical outcomes will also be documented.

Center and Operator Characteristics

Participating center and operator characteristics relevant to CTO PCI will be recorded, including operator CTO PCI experience and annual CTO PCI volume. Procedures performed with proctor support will also be identified. These data will allow evaluation of potential associations between operator and center experience, procedural strategy, efficiency, success, and complications.

Angiographic and CTO Lesion Characteristics

Detailed angiographic assessment will include the CTO target vessel and segment, occlusion characteristics, proximal cap morphology, distal vessel characteristics, lesion length, vessel diameter, calcification, tortuosity, side branches, collateral circulation, previous stenting when applicable, and other anatomical characteristics relevant to CTO PCI.

Established CTO complexity and procedural prediction scores will be recorded or calculated when applicable to allow assessment of lesion complexity and prediction of procedural outcomes.

CTO PCI Strategies and Techniques

Detailed procedural data will be collected for the entire CTO PCI procedure. Initial and final crossing strategies, changes in strategy during the procedure, and reasons for strategy modification or procedural failure will be documented.

Antegrade wire escalation, antegrade dissection and re-entry, retrograde techniques, and hybrid CTO PCI strategies will be evaluated. For retrograde procedures, collateral channel selection, septal or epicardial collateral use, collateral crossing, retrograde wire and microcatheter techniques, reverse controlled antegrade and retrograde tracking and other re-entry techniques will be recorded where applicable.

The registry will capture the sequence, purpose, and procedural performance of CTO guidewires and microcatheters used during the intervention. Information regarding specialized CTO guidewires, conventional and dual-lumen microcatheters, guide-extension catheters, re-entry devices, and other dedicated CTO equipment will be collected.

Lesion Preparation, Imaging, and Adjunctive Technologies

Information regarding balloon angioplasty, stent implantation, lesion preparation, and management of resistant or calcified lesions will be recorded. Use of specialized technologies and calcium-modification strategies, including high-pressure balloons, scoring or cutting balloons, intravascular lithotripsy, atherectomy, and other adjunctive techniques, will be documented when applicable.

Use of intravascular imaging, including intravascular ultrasound and other imaging modalities when performed, will also be recorded, together with their role in procedural guidance, optimization, and assessment of complications.

Procedural Efficiency and Radiation Exposure

Procedural performance will be evaluated using parameters including total procedure duration, fluoroscopy time, radiation exposure, contrast volume, and anticoagulation-related procedural parameters, including activated clotting time where available.

These data will permit evaluation of factors associated with procedural efficiency, radiation burden, contrast utilization, and the relationship between procedural complexity and resource utilization.

Procedural Success

Technical and procedural success will constitute major outcomes of the registry. Successful CTO crossing and restoration of antegrade coronary flow, residual stenosis, achievement of the intended revascularization result, and the occurrence or absence of significant procedure-related adverse events will be evaluated according to predefined registry definitions.

The registry will investigate clinical, angiographic, anatomical, technical, device-related, operator-related, and procedural predictors of successful and unsuccessful CTO PCI.

Procedural and In-Hospital Complications

Periprocedural and in-hospital adverse events will be systematically recorded. These will include coronary perforation of varying severity, pericardial effusion and cardiac tamponade, coronary dissection, donor-vessel injury, collateral channel injury, side-branch loss, acute vessel closure, vascular access complications, bleeding events, myocardial infarction, stroke, emergency cardiac surgery, acute kidney injury, and death, as applicable.

Other clinically relevant CTO PCI-related complications and their management will also be documented.

Clinical Outcomes and Follow-up

Clinical follow-up will be performed according to the registry protocol to evaluate cardiovascular outcomes after CTO PCI. Outcomes of interest will include all-cause and cardiovascular mortality, myocardial infarction, stroke, repeat coronary revascularization, target-vessel and target-lesion revascularization, subsequent PCI or coronary artery bypass graft surgery, and other major adverse cardiovascular events.

Where available, additional clinically relevant outcomes, including recurrence or persistence of symptoms, subsequent hospitalization, and the need for further coronary intervention, will be assessed.

Both individual clinical events and relevant composite cardiovascular endpoints will be analyzed. The registry will also investigate predictors of adverse clinical outcomes during follow-up and evaluate the relationship between procedural success, procedural strategy, complications, and subsequent clinical outcomes.

Observational Design

The TURK CTO Registry is strictly observational. The study protocol will not assign or mandate a specific revascularization strategy, guidewire, microcatheter, device, vascular access route, imaging modality, pharmacological treatment, or procedural technique. Patient selection and all diagnostic, therapeutic, and procedural decisions will remain at the discretion of the treating physicians and CTO operators in accordance with routine clinical practice.

Data will be collected using a standardized electronic case report form. Participating investigators and centers will be responsible for accurate and complete data entry. Standardized definitions and predefined data-quality procedures will be used to promote consistency and reliability across participating centers.

Over its planned 10-year duration, the TURK CTO Registry is expected to provide a comprehensive assessment of the evolution of CTO PCI practice in Türkiye, including changes in patient selection, procedural strategies, devices, technologies, success rates, safety, and clinical outcomes. The registry will facilitate the identification of predictors of procedural success and failure, complications, radiation and contrast burden, and adverse cardiovascular outcomes, and will provide a platform for future studies aimed at improving the safety, effectiveness, and quality of CTO PCI.