Prophylactic IABP in Delayed-Presentation Anterior STEMI

This is a prospective, multicenter, randomized, open-label, parallel-group, controlled clinical trial with blinded endpoint adjudication. The study is designed to evaluate whether prophylactic intra-aortic balloon counterpulsation (IABP) before primary percutaneous coronary intervention (PPCI) can improve outcomes in patients with delayed-presentation acute anterior ST-segment elevation myocardial infarction (STEMI). Eligible patients are adults aged ≥18 years with symptom onset to presentation between 4 and 12 hours, electrocardiographic evidence of anterior STEMI (≥2 mm ST elevation in contiguous anterior leads or sum ≥4 mm), and angiographically confirmed proximal left anterior descending artery occlusion with TIMI flow 0. After informed consent and coronary angiography confirming eligibility, participants are randomized in a 1:1 ratio to one of two groups: (1) prophylactic IABP before infarct-related artery opening plus standard PPCI, or (2) standard PPCI alone. In the intervention group, IABP will be inserted before PCI, operated at a 1:1 counterpulsation ratio for at least 24 hours and up to 72 hours as clinically appropriate. In the control group, prophylactic mechanical circulatory support will not be routinely used; rescue IABP may be initiated if predefined hemodynamic deterioration or complications occur. All participants receive guideline-directed medical therapy for ST-segment elevation myocardial infarction. The primary endpoint is major adverse cardiovascular events (MACE) within 180 days after randomization, defined as a composite of all-cause death, cardiogenic shock, and new or worsening heart failure. Secondary endpoints include individual components of the primary composite endpoint, cardiac death, length of hospital stay, NT-proBNP at 90 and 180 days, left ventricular ejection fraction and left ventricular end-diastolic volume at 90 and 180 days. Safety outcomes include major bleeding (BARC 3-5), vascular complications, thrombocytopenia, and stroke within 30 days. Follow-up assessments will be performed during hospitalization and at 30, 90, and 180 days after randomization. Endpoint adjudication will be performed by an independent clinical events committee blinded to treatment assignment.

Inclusion criteria

• Age ≥ 18 years.
• First electrocardiogram on arrival shows ST-segment elevation ≥ 2 mm in at least two contiguous anterior leads, or sum of ST-segment elevation ≥ 4 mm in anterior leads.
• Ischemic symptoms (chest pain, chest tightness, upper abdominal discomfort, left shoulder radiation, etc.) onset to hospital arrival between ≥ 4 hours and ≤ 12 hours, and planned for primary PCI.
• Coronary angiography confirms the infarct-related artery is the proximal left anterior descending (LAD) (before the first septal branch or first diagonal branch) with TIMI flow grade 0 (total occlusion).
• Patient or legal representative provides written informed consent.

Exclusion criteria

• Established cardiogenic shock (systolic blood pressure < 90 mmHg without inotropes/vasopressors, or requiring vasopressors to maintain systolic blood pressure ≥ 90 mmHg, AND blood lactate > 2.0 mmol/L).
• Severe heart failure: Killip class ≥ III, or requiring non-invasive/invasive positive pressure ventilation before enrollment.
• Malignant arrhythmias, including cardiac arrest, ventricular fibrillation, ventricular flutter, pulseless ventricular tachycardia, or high-grade atrioventricular block.
• Severe mechanical complications (e.g., free wall rupture, ventricular septal defect, acute severe mitral regurgitation).
• Contraindications to IABP (severe peripheral vascular disease, aortic dissection, known aortic aneurysm, moderate-to-severe aortic regurgitation).
• Prior myocardial infarction or known chronic heart failure (left ventricular ejection fraction < 50%).
• Prior coronary artery bypass grafting (CABG).
• Stroke within 1 month, or history of hemorrhagic stroke at any time.
• Active gastrointestinal bleeding within 3 months, or gastrointestinal diseases with increased bleeding risk.
• Received thrombolytic therapy for this episode.
• Initiation of any mechanical circulatory support (IABP, Impella, ECMO) before coronary angiography.
• Severe hepatic insufficiency (Child-Pugh C, or ALT >5×ULN with total bilirubin >3×ULN), renal insufficiency (eGFR < 15 mL/min/1.73 m² or chronic dialysis), or end-stage disease with life expectancy < 1 year.
• Pregnancy or lactation.
• Currently participating in another interventional trial.