①Research objective: In a small sample population, through the pre - experimental method, explore and evaluate the effect of Guanxinning tablets on the coronary microcirculation after primary percutaneous coronary intervention (PPCI) in patients with acute ST - segment elevation myocardial infarction (STEMI), with the change in the percentage of intramyocardial hemorrhage (IMH) in ventricular mass measured by cardiac magnetic resonance (CMR) imaging as the primary endpoint.

②Research significance: The research results of this project will provide preliminary theoretical basis and methodological support for the formal randomized controlled study on evaluating the effect of Guanxinning tablets on the coronary microcirculation after PPCI in STEMI patients. It will offer new ideas for the long - term clinical treatment of STEMI patients after PPCI, and provide important theoretical support for expanding the clinical indications of Guanxinning tablets and exploring the reasons for its improvement of cardiovascular outcomes.

This study is a preliminary pre-trial for a single-center, prospective, randomized, double-blind, placebo-controlled trial. The objective is to explore the effect of Guanxinning Tablet on improving coronary microcirculation. A total of 70 STEMI patients who have successfully undergone primary percutaneous coronary intervention (PPCI) will be enrolled. Regardless of whether elective complete revascularization is needed, after the IRA (infarct-related artery) is treated during PPCI, patients will be randomly assigned in a 1:1 ratio to two groups: one group will receive an immediate loading dose of 4 Guanxinning Tablets post-PPCI, followed by a maintenance dose of 4 tablets three times daily (TID) (intervention group), while the other group will receive placebo treatment (placebo group). Both groups will receive standard secondary prevention treatment for coronary heart disease. Patients in both groups will undergo cardiac magnetic resonance (CMR) examinations within 1 week after PPCI and at 6 months (±14 days) post-PPCI.

Primary Endpoint:

The change in the percentage of intramyocardial hemorrhage (IMH) volume relative to ventricular volume in the IRA-supplied myocardial territory, measured by CMR at the 6-month follow-up.

Secondary Endpoints:

• Change in the incidence of IMH in the IRA-supplied myocardial territory measured by CMR at 6 months.

  • Change in the percentage of microvascular obstruction (MVO) volume in the IRA-supplied myocardial territory measured by CMR at 6 months.

    • Change in the incidence of MVO in the IRA-supplied myocardial territory measured by CMR at 6 months.

      • Change in myocardial infarct size and percentage of myocardial edema volume measured by CMR at 6 months.

        • Change in left ventricular ejection fraction (LVEF) measured by echocardiography at 6 months.

          • Change in angina pectoris score at 6 months. ⑦ Change in traditional Chinese medicine (TCM) syndrome score for blood stasis pattern at 6 months.

            • Association between changes in circulating inflammatory markers (oxidized LDL, IL-6, hsCRP) and diabetes markers (HbA1c, FBG, GSP) at 6 months with coronary microcirculation status.

Safety Endpoints:

Composite endpoint including all-cause mortality, non-fatal myocardial infarction, non-fatal stroke, ischemia-driven repeat revascularization, rehospitalization for heart failure, and any drug-related adverse reactions.

Inclusion Criteria:

• Age between 18 and 80 years (gender is not restricted).
• STEMI diagnosed for the first time and with an onset time within 12 hours. (According to the "Chinese Guidelines for the Diagnosis and Treatment of Acute ST - Segment Elevation Myocardial Infarction 2019" and the fourth - edition "Global Definition of Myocardial Infarction" criteria, myocardial infarction refers to acute myocardial injury [serum cardiac troponin (cTn) increases and/or decreases, and at least once is higher than the upper limit of the normal value (the 99th percentile of the upper limit of the reference value)], along with clinical evidence of acute myocardial ischemia, including: (1) Symptoms of acute myocardial ischemia; (2) New ischemic electrocardiogram changes; (3) New pathological Q - wave; (4) New imaging evidence of viable myocardial loss or abnormal wall segmental motion; (5) Coronary artery thrombosis confirmed by coronary angiography, intracavitary imaging examination, or autopsy.)
• Successfully received PPCI treatment (assessed by visual inspection or quantitative coronary angiography, with residual stenosis of the target lesion < 20% after stent implantation or < 50% after simple balloon dilation, and forward TIMI blood flow ≥ grade 2).
• Signed a written informed consent form.

Exclusion Criteria:

• Cardiogenic shock with poor response to vasoactive drugs; or uncontrolled acute left - heart failure or pulmonary edema; uncontrolled malignant arrhythmia.
• LVEF < 40%.
• Currently using nicorandil, other Chinese patent medicines, and Chinese herbal decoctions, etc.
• Unable to undergo CMR examination for various reasons.
• Expected to be unable to complete 6 - month treatment with Guanxinning Tablets.
• Contraindications or allergies to Guanxinning Tablets.
• Suspected or confirmed hereditary cardiomyopathy (such as hypertrophic, dilated, obstructive cardiomyopathy, cardiac amyloidosis, hemochromatosis cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, etc.).
• Active or chronic liver disease.
• Renal insufficiency (eGFR < 60ml/min/1.73m²).
• History of previous cerebral hemorrhage.
• History of alcohol or drug abuse.
• Known active infection, or severe hematological, metabolic, or endocrine dysfunction.
• Patients who have received systemic steroid or cyclosporine treatment in the past 3 months.
• Active malignant tumor.
• Life expectancy less than 6 months.
• Pregnant or lactating women.
• Already participating in other clinical studies.