The study intends to evaluate the efficacy of different medicine delivering by targed perfusion catheter incoronary administration on epicardial, myocardial perfusion and clinical outcomes in STEMI patients undergoing primary PCI.

The goal of STEMI therapy is to successfully restore both epicardial blood flow and myocardial perfusion. PCI has been documented as being the most effective method for restoration of epicardial blood flow. However, epicardial blood flow does not necessarily equate to myocardial perfusion; not every patient with TIMI 3 flow after successful PCI achieves effective myocardial tissue-level perfusion. Although epicardial TIMI 3 flow could be restored in >90% of STEMI patients undergoing PCI, normalization of myocardial perfusion was achieved less frequently, with detrimental impacts on survival。 Currently, there are two main methods of angiographic assessment of myocardial perfusion: TIMI myocardial perfusion grading (TMPG), described by Gibson et al. and myocardial blush grading (MBG), described by Van't Hof et al. These established myocardial perfusion parameters, TMPG and MBG, have been widely used in various important trials and are reported to be highly useful in predicting clinical outcomes. However, visual assessment of these methods is categorical, subjective, and operator dependent. TIMI Myocardial Perfusion Frame Count (TMPFC), a novel and objective method that measures the filling and clearance of contrast in the myocardium using cine-angiographic frame-counting, was developed by our center to quantify myocardial tissue- level perfusion and was proved to be a predictive value on clinical prognosis.

Currently, there are two main types of interventions to improve myocardial perfusion . One kind is the mechanical method, which included thrombus aspiration catheter and the distal protective devices. It has been confirmed that the mechanical method can effectively improve epicardial and myocardial perfusion in patient with part of large vessels and high burden thrombus. But for patients with small vessels and no obvious visual thrombus, the efficacy is not significant.

The other kind intervention is medicine which included GP IIb/IIIa receptor antagonist , adenosine , sodium nitroprusside, verapamil etc. Part of the drugs have some effect but the overall clinical efficacy is still not satisfied.

The study intends to use targeted perfusion catheter to deliver drug to the distal targeted blood vessels. TMPFC and TMPG are applied to evaluate the efficacy of treatment with Nicorandil versus Alprostadil on myocardial tissue-level perfusion in STEMI patients undergoing primary PCI.

Inclusion Criteria:

• Age: over 18 or 18 years old, less than 75 years old;
• Patents with myocardial infarction who have symptom onset within 6h before randomization;
• ECG: ≥2 mm ST-segment elevation in 2 contiguous precordial leads or ≥1 mm ST-segment elevation in 2 contiguous extremity leads ;
• Signed informed consent form prior to trial participation.

Exclusion Criteria:

1. Evidence of cardiac rupture;

2. ECG: new left bundle branch block;

3. Thrombolysis contradictions:

4. Severe complication

   • Other diseases with life expectancy ≤12 months;
   • Any history of Severe renal or hepatic dysfunction(hepatic failure, cirrhosis, portal hypertension and active hepatitis); Neutropenia, thrombocytopenia ; Known acute pancreatitis;
   • Known acute pericarditis and/or subacute bacterial endocarditis;
   • Arterial aneurysm, arterial/venous malformation and aorta dissection;

5. Complex heart condition

   • Cardiogenic shock(SBP <90 mmHg after fluid infusion or SBP<100 mmHg after vasoactive drugs);
   • PCI within previous 1 month or Previous coronary-artery bypass surgery(CABG);
   • Previously known multivessel coronary artery disease not suitable for revascularization;
   • Hospitalisation for cardiac reason within past 48 hours;

6. Not suitable for clinical trial

   • Inclusion in another clinical trial;
   • Previous enrolment in this study or treatment with an investigational drug or device under another study protocol in the past 7 days;
   • Pregnancy or lactating;
   • Body weight <40kg or >125kg;
   • Known hypersensitivity to any drug that may appear in the study;
   • Inability to follow the protocol and comply with follow-up requirements or any other reason that the investigator feels would place the patient at increased risk.