This is a prospective, multicenter, observational registry designed to evaluate clinical outcomes in patients undergoing complex high-risk indicated percutaneous coronary intervention (CHIP-PCI) in China. Eligible patients will be adults with complex coronary artery disease and severely reduced left ventricular function, or reduced left ventricular function with severe mitral regurgitation, who are considered by the heart team to have an indication for coronary revascularization but are at high risk for coronary artery bypass grafting or decline surgical revascularization.

The registry will collect baseline clinical characteristics, coronary angiographic and procedural data, use of intravascular imaging or physiological assessment, revascularization strategy, mechanical circulatory support, peri-procedural complications, laboratory and echocardiographic data, and follow-up outcomes. The primary endpoint is all-cause mortality at 1 year after PCI. Secondary endpoints include major adverse cardiovascular events, cardiac death, myocardial infarction, target vessel revascularization, heart failure hospitalization, major bleeding, and quality-of-life measures. The study also aims to identify prognostic factors and develop a risk prediction model for patients undergoing CHIP-PCI.

Complex high-risk indicated patients undergoing percutaneous coronary intervention represent a clinically challenging population. These patients often have complex coronary anatomy, impaired cardiac function, hemodynamic vulnerability, advanced age, frailty, or multiple comorbidities. Although advances in interventional techniques, adjunctive devices, intravascular imaging, physiological assessment, and mechanical circulatory support have expanded the feasibility of PCI in this population, evidence regarding optimal treatment strategies and long-term outcomes remains limited, particularly in real-world Chinese practice.

This study is a prospective, multicenter, observational registry conducted in tertiary hospitals with experience in complex high-risk PCI. The study will enroll approximately 1,000 patients who meet the predefined eligibility criteria and undergo PCI as part of routine clinical care. No additional interventional treatment will be mandated by the protocol. PCI strategy, use of intravascular imaging such as IVUS or OCT, physiological assessment such as FFR or QFR, lesion preparation techniques, complete or incomplete revascularization, staged PCI, antithrombotic therapy, and the use and type of mechanical circulatory support will be determined by the treating physicians according to contemporary guidelines, expert consensus, and local clinical practice.

Eligible patients include adults aged 18 to 90 years who are considered by the heart team to have an indication for coronary revascularization but are at high risk for coronary artery bypass grafting or decline CABG, and for whom PCI is considered beneficial. Patients are required to have left ventricular ejection fraction ≤35%, or left ventricular ejection fraction ≤40% with severe mitral regurgitation, together with complex PCI features such as unprotected left main disease, last remaining patent coronary artery PCI, three-vessel disease, heavily calcified lesions requiring rotational atherectomy, or chronic total occlusion requiring bilateral angiography or retrograde techniques. Patients with acute ST-segment elevation myocardial infarction within 1 week, cardiogenic shock, inability to complete follow-up, or other conditions considered unsuitable by investigators will be excluded.

Data collection will include demographic characteristics, medical history, comorbidities, medication use, cardiac function, physical examination, laboratory tests, electrocardiography, echocardiography, quality-of-life assessments, coronary angiography, lesion characteristics, procedural details, use of intravascular imaging or physiological assessment, lesion preparation, mechanical circulatory support, procedural success, completeness of revascularization, residual SYNTAX score, and peri-procedural complications. Follow-up will be performed at 1 month, 3 months, 6 months, 1 year, and 2 years after PCI by outpatient visit or telephone contact. Quality-of-life assessments will be collected at 3 months, 6 months, 1 year, and 2 years. Clinical events suggestive of cardiovascular outcomes, including chest pain, myocardial infarction, heart failure, or other cardiovascular hospitalization, will be recorded and adjudicated according to predefined endpoint definitions.

The primary endpoint is all-cause mortality at 1 year after PCI. Secondary endpoints include 1-year major adverse cardiovascular events, defined as a composite of all-cause death, myocardial infarction, target vessel revascularization, and heart failure hospitalization; cardiac death; myocardial infarction; target vessel revascularization; heart failure hospitalization; major bleeding defined as BARC type 3 or 5 bleeding; and quality-of-life scores. Additional analyses will evaluate the association between clinical, anatomical, procedural, imaging, physiological, and mechanical circulatory support variables and clinical outcomes. The registry will also be used to develop a risk prediction model to support clinical decision-making in patients undergoing CHIP-PCI.

This registry is expected to provide real-world evidence on contemporary CHIP-PCI practice in China, including patient characteristics, procedural strategies, use of adjunctive technologies, short- and long-term outcomes, and predictors of adverse events. The findings may help optimize risk stratification, procedural planning, and post-PCI management in complex high-risk patients.

Inclusion Criteria:

Participants must meet all of the following criteria:

1. Age 18 to 90 years.

2. Willing and able to comply with the study protocol and data collection procedures, able to understand the purpose of the study, and willing to provide written informed consent.

3. Considered by the heart team to have an indication for coronary revascularization but to be at high risk for coronary artery bypass grafting, or the patient declines coronary artery bypass grafting, and PCI is considered potentially beneficial after heart team evaluation.

4. Left ventricular ejection fraction ≤35%, or left ventricular ejection fraction ≤40% with severe mitral regurgitation.

5. Undergoing complex PCI with at least one of the following features:

   • Unprotected left main coronary artery disease;
   • PCI of the last remaining patent coronary artery;
   • Three-vessel coronary artery disease;
   • Calcified coronary lesion requiring rotational atherectomy;
   • Chronic total occlusion requiring bilateral angiography or retrograde techniques.

Exclusion Criteria:

Participants meeting any of the following criteria will be excluded:

1. Acute ST-segment elevation myocardial infarction within 1 week before enrollment.

2. Cardiogenic shock, defined by all of the following:

   • Systolic arterial blood pressure <90 mmHg for ≥30 minutes, or need for vasopressors, inotropes, or mechanical circulatory support to maintain systolic arterial blood pressure ≥90 mmHg;
   • Evidence of reduced cardiac output, such as cardiac index <2.2 L/min/m²;
   • Evidence of end-organ hypoperfusion, including cold extremities, urine output <30 mL/hour, altered mental status, or lactate >2 mmol/L.

3. Unable to complete the planned follow-up.

4. Any other condition that, in the opinion of the investigator, makes the patient unsuitable for participation in the registry.

The study population will consist of adult patients with complex high-risk indicated coronary artery disease undergoing percutaneous coronary intervention in routine clinical practice at participating tertiary hospitals in China. Eligible patients will have complex coronary anatomy and impaired left ventricular function, and will be considered by the heart team to have an indication for coronary revascularization but to be at high risk for coronary artery bypass grafting or to have declined surgical revascularization. PCI strategy, adjunctive imaging or physiological assessment, revascularization approach, antithrombotic therapy, and use of mechanical circulatory support will be determined by the treating physicians according to clinical judgment and local practice. This is an observational registry and no study-mandated intervention will be assigned.