DSMB halted the study due to safety concerns.

Timely percutaneous coronary intervention (PCI) with stenting implantation is the current standard treatment for patients with ST-segment elevation myocardial infarction (STEMI). However, stenting in thrombus-laden artery is associated with higher risk of embolization and no-or slow-reflow, leading to larger infarct size and poor prognosis. The SALVAGE study is a prospective, multicenter, randomized, controlled study aimed to optimize the therapeutic strategies (deferred vs. immediate stenting) to protect microvascular function and eventually improve clinical outcomes at 12-months in STEMI.

Methodology:

A multicenter, prospective, randomized, controlled clinical study enroll patients with ST-segment elevation myocardial infarction (STEMI) intended for PCI with stenting implantation. Eligible patients are randomly assigned to the immediate stenting group or delayed stenting group in a 1:1 ratio when residual stenosis >70% and TIMI grade 3 with angiography guidance.

The index of microcirculation resistance (IMR) is quantitative analysis by an invasive approach for evaluating post-infarct myocardial microcirculatory perfusion. IMR correlates with the infarct size of patients with acute myocardial infarction and predicts the improvement in left ventricular ejection fraction. Studies have shown that acute myocardial infarction patients with IMR >40 after primary PCI predict adverse long-term clinical outcomes with higher mortality and heart failure rehospitalization rates.

According to therapeutic strategies and microvascular function detected by IMR, participants are classified into four groups: immediate stenting with IMR ≥ 40, immediate stenting with IMR < 40, deferred stenting with IMR ≥ 40 and deferred stenting with IMR < 40. All randomized patients will be followed by phone call or clinical visit at 12 months.

Patient enrollment and procedure overview:

Patients aged from 18 to 80 with STEMI<12h in whom PCI is planned will be screened. Thrombectomy and balloon dilatation will be performed at the operator's discretion to restore an effective antegrade blood flow with TIMI flow grade 3. Patients with residual diameter stenosis >70% visually and TIMI blood flow grade 3 are eligible for including in the study. All patients must provide written informed consent and patients will be randomized to immediate stenting group or deferred stenting group in a 1:1 ratio. All participants in immediate stenting group will be treated with stent implantation immediately. Those assigned to the deferred arm will undergo stenting after an interval of 7±2 days. This interval will be bridged with anti-coagulant and anti-platelet therapy to reduce thrombus burden. All patients in both groups are required to take dual antiplatelet treatment while the application of low molecular weight heparin and glycoprotein IIb/IIIa inhibitor are determined by the operators. All participants are required to perform IMR pre-stenting and post-stenting to evaluate microcirculation function. All randomized patients will be followed up to 12 months to evaluate the prevalence of heart failure, all-cause mortality, recurrent infarction or targeted vessel revascularization.

Study follow-up:

Clinical follow-up:

Participants will be followed by phone calls or clinical visits by study coordinators at 1 month (+/-7 days), 3 months (+/-15 days), 6 months (+/-15 days), 9 months (+/-15 days) and 12 months (+/-30 days) after randomization. Major adverse cardiovascular events (MACEs) will be recorded throughout the study period until last patient has been followed for 12 months.

Inclusion Criteria:

• 18 years old ≤ age ≤ 80 years old;
• STEMI and the onset time <12h;
• The culprit lesions are de novo lesion;
• Sign written informed consent.

Exclusion Criteria:

• Patients are hemodynamically unstable;
• Infract-related artery diameter stenosis ≤ 70%;
• Left main disease;
• AMI caused by surgery, trauma, gastrointestinal bleeding or PCI and complications;
• AMI occurs in patients who have been hospitalized for other reasons;
• The investigator judges that the patient has poor compliance and cannot complete the study as required;
• Life expectancy ≤ 12 months;
• Heart transplant patients;
• Definite diagnosis of patients with tumors;
• Participate in other clinical studies (excluding other trials of this project) and haven't reach the primary endpoints.