Prophylactic IABP in Delayed-Presentation Anterior STEMI

Inclusion Criteria: 1. Age ≥ 18 years. 2. 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. 3. 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. 4. 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). 5. Patient or legal representative provides written informed consent. Exclusion Criteria: 1. 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). 2. Severe heart failure: Killip class ≥ III, or requiring non-invasive/invasive positive pressure ventilation before enrollment. 3. Malignant arrhythmias, including cardiac arrest, ventricular fibrillation, ventricular flutter, pulseless ventricular tachycardia, or high-grade atrioventricular block. 4. Severe mechanical complications (e.g., free wall rupture, ventricular septal defect, acute severe mitral regurgitation). 5. Contraindications to IABP (severe peripheral vascular disease, aortic dissection, known aortic aneurysm, moderate-to-severe aortic regurgitation). 6. Prior myocardial infarction or known chronic heart failure (left ventricular ejection fraction \< 50%). 7. Prior coronary artery bypass grafting (CABG). 8. Stroke within 1 month, or history of hemorrhagic stroke at any time. 9. Active gastrointestinal bleeding within 3 months, or gastrointestinal diseases with increased bleeding risk. 10. Received thrombolytic therapy for this episode. 11. Initiation of any mechanical circulatory support (IABP, Impella, ECMO) before coronary angiography. 12. 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. 13. Pregnancy or lactation. 14. Currently participating in another interventional trial.