The goal of this clinical trial is to learn if adding standardized manual thrombus aspiration to primary percutaneous coronary intervention (PPCI) works better to improve heart health outcomes and protect long-term heart function in adults with acute ST-segment elevation myocardial infarction (STEMI) and a high blood clot burden in the heart's arteries. The main questions it aims to answer are:

• Does PPCI plus manual thrombus aspiration lower the risk of serious heart problems one year after treatment, compared to PPCI alone?
• Can manual thrombus aspiration better protect long-term heart function in people with a high blood clot burden? Researchers will compare two groups of participants-one group getting PPCI plus manual thrombus aspiration and one group getting only PPCI-to see if the aspiration treatment leads to fewer serious heart problems, better long-term heart function, and similar safety (including no higher risk of stroke).

Participants will:

• Have a heart artery scan (coronary angiography) to confirm a high blood clot burden
• Be randomly assigned to one of the two treatment groups for their PPCI procedure
• Complete follow-up checks at 30 days, 6 months, and 1 year after treatment, including heart function tests (like echocardiograms)
• Have heart magnetic resonance (CMR) scans if selected, to measure heart tissue damage and heart function
• Have their heart health status and any adverse events recorded throughout the study

This study is a multicenter, randomized, controlled, single-blind clinical trial designed to explore the clinical value of manual thrombus aspiration in the treatment of acute ST-segment elevation myocardial infarction (STEMI) patients with high thrombus burden, and to fill the current critical evidence gap in this field.

Study Background The core pathophysiology of STEMI is coronary atherosclerotic plaque rupture followed by thrombosis that leads to complete vascular occlusion, making primary percutaneous coronary intervention (PPCI) the first-line reperfusion strategy. However, conventional PPCI may cause no-reflow or slow-reflow phenomena, partly due to distal microvascular embolization caused by thrombus or plaque debris shedding during the operation. Based on this, thrombus aspiration was developed, which is intended to directly remove thrombus with a negative pressure suction device before PPCI, theoretically restoring coronary antegrade blood flow, reducing distal embolization, improving myocardial perfusion, and thus protecting left ventricular function and clinical prognosis. Early studies and meta-analyses showed encouraging results for thrombus aspiration, leading to its wide clinical adoption and inclusion in STEMI management guidelines of the European Society of Cardiology (ESC) and American Heart Association (AHA) as a Class II recommendation with Level A evidence. However, the publication of results from large-scale randomized controlled trials (RCTs) such as TASTE and TOTAL has led to controversial conclusions about routine thrombus aspiration, even resulting in its non-recommendation in relevant European and American guidelines. This has created a clinical paradox: thrombus aspiration is necessary for a considerable proportion of STEMI patients to achieve effective coronary blood flow and subsequent stent implantation, yet the operation lacks clear guideline recommendations, laying the foundation for the launch of this study (TRAP-MI).

Research Progress at Home and Abroad The clinical research and application of thrombus aspiration for STEMI have experienced three stages: support and hope, challenge and turning point, and controversy and re-exploration. The landmark 2008 TAPAS study, the first single-center RCT, confirmed that manual thrombus aspiration significantly improved myocardial perfusion grade and ST-segment resolution rate, and reduced 1-year all-cause and cardiac mortality compared with PPCI alone, greatly promoting its clinical application. The 2013 TASTE study and 2015 TOTAL study, as large-scale multicenter RCTs, reported neutral results for routine thrombus aspiration, with the TOTAL study even finding a significantly increased 30-day stroke incidence in the aspiration group, leading to the downgrade of thrombus aspiration recommendations in European and American guidelines to "not recommended for routine use". In the subsequent controversy and re-exploration stage, researchers found design flaws in these negative RCTs that may have masked the benefits of thrombus aspiration, such as randomization before angiography and a high rate of rescue aspiration in the control group. Post-hoc subgroup analyses suggested a potential benefit trend of thrombus aspiration in patients with high thrombus burden (TIMI thrombus grade ≥3), who accounted for 90% of enrolled patients in the TOTAL study. Additionally, observational studies and meta-analyses in East Asian populations (China and South Korea) indicated a possible association between thrombus aspiration and reduced mortality, and modern aspiration catheters have overcome the limitations of early devices in passability and suction efficiency. Current clinical consensus holds that routine thrombus aspiration is not recommended for all STEMI patients, but it may be beneficial for specific high-risk subgroups, though this lacks high-quality evidence from large-scale prospective RCTs.

Study Significance

• Precise population positioning: This study abandons the "one-size-fits-all" approach and focuses on STEMI patients with angiographically confirmed high thrombus burden, the subgroup most likely to benefit from thrombus aspiration, realizing the transformation from empirical treatment to precision medicine.
• Evaluation of modern devices and standardized operations: The study adopts the latest generation of aspiration catheters with better passability and suction efficiency, and formulates strict standardized operation procedures to maximize thrombus removal effect and minimize operation-related complications such as stroke, making up for the limitations of early studies in device and operation standardization.
• Focus on myocardial salvage and long-term cardiac function: In addition to traditional hard endpoints such as death and recurrent myocardial infarction, the study sets rich intermediate endpoints including myocardial salvage index, microvascular obstruction range, and left ventricular ejection fraction changes, which can more comprehensively verify the protective effect of thrombus aspiration on myocardial microcirculation and long-term cardiac function.
• Provision of high-quality evidence for the Chinese population: As a multicenter clinical trial conducted in the Chinese population, the study will verify the efficacy and safety of thrombus aspiration in Chinese STEMI patients with high thrombus burden, providing the highest level of evidence-based medical evidence for formulating clinical practice guidelines suitable for China's national conditions.

Key Problems to Be Solved

Based on the current research status and clinical needs, this study intends to solve the following key scientific and clinical problems:

• Efficacy key problem: In STEMI patients with angiographically confirmed high thrombus burden undergoing PPCI, can combined standardized modern manual thrombus aspiration significantly reduce the incidence of major adverse cardiovascular events (MACEs) (including cardiovascular death, recurrent myocardial infarction, target vessel revascularization, and rehospitalization for heart failure) compared with PPCI alone?
• Mechanism key problem: Can thrombus aspiration effectively improve myocardial level perfusion, as evidenced by significantly increased myocardial salvage index, reduced final infarct size and microvascular obstruction range confirmed by cardiac magnetic resonance (CMR)?
• Safety key problem: With the use of the new generation of aspiration catheters and standardized operation procedures, is the risk of stroke and other surgical complications (such as coronary dissection and perforation) related to thrombus aspiration not significantly different from that of the control group, thus responding to the concern about increased stroke risk in the TOTAL study?
• Long-term prognosis key problem: Can thrombus aspiration bring long-term cardiac function protection to patients with high thrombus burden, manifested as better improvement of left ventricular ejection fraction and ventricular configuration at 6 months to 1 year after surgery?

Inclusion Criteria:

• Aged ≥18 years old, diagnosed with acute ST-segment elevation myocardial infarction (STEMI) (chest pain plus ST-segment elevation ≥1mm or new-onset left bundle branch block [LBBB]) with symptom onset < 12 hours.
• Planned to undergo primary percutaneous coronary intervention (PPCI).
• High thrombus burden in the target vessel (TIMI thrombus grade ≥3, or visible floating thrombus) confirmed by coronary angiography.
• Reference diameter of the target vessel ≥2.75mm, with the lesion suitable for the passage of an aspiration catheter.
• Provided written informed consent to participate in the study.

Exclusion Criteria:

• Cardiogenic shock (Killip class IV) or requiring mechanical circulatory support.
• A history of previous coronary artery bypass grafting (CABG).
• Concurrent intervention required for non-culprit vessels.
• Severe bleeding tendency (e.g., INR > 2.5, platelet count < 50×10⁹/L).
• Severe renal insufficiency (estimated glomerular filtration rate [eGFR] < 30 ml/min/1.73m²).
• Expected survival time < 1 year (e.g., advanced malignant tumor).