Percutaneous coronary intervention for myocardial infarction with ST elevation could be complicated with thrombus embolisation to the more distal segments of the culprit artery. Hypothesis - lower injection pressure could reduce the incidence of this complication. In this study the investigators compare two different protocols for dye injection - first one with higher and the second one with lower injection pressure.The impact of different pressure will be evaluated using the estimation of completeness of resolution of ST elevation as well as Myocardial Blush Grade on the end of the procedure. Patents will be followed for in-hospital mortality and MACE.

Distal embolization of plaque and thrombotic debris in the infarct-related artery may lead to microvascular obstruction resulting in impaired myocardial reperfusion. The aim of the study was to assess the impact of contrast injection pressure in coronary arteries, during primary percutaneous coronary intervention (PCI), on myocardial reperfusion in patients with acute ST-segment elevation myocardial infarction (STEMI).

A randomized, prospective, open label, pilot study. In the period of 6 months, consecutive patients with acute STEMI were included in the study. The acute STEMI was confirmed according to the clinical, ECG and cardioselective enzymes criteria.

Patients with the following features were eligible for inclusion: who underwent primary PCI within 12 hours from the onset of symptoms, with typical chest pain lasting >30 minutes, with ST-segment elevation of ≥1 mm in ≥2 contiguous leads in ECG and with ECGs recorded at admission, 60 minutes and 24h after primary PCI.

Exclusion criteria were: patients who had cardiogenic shock and/or underwent cardiopulmonary resuscitation before or during primary PCI, with symptoms lasting more than 12 hours, with left bundle branch block in ECG at admission, with diameter stenosis < 50% of the culprit lesion or normal coronary blood flow, with severe left main coronary artery or multivessel disease who required emergency cardiac-surgery revascularization, with permanent cardiac pacemaker or implantable cardioverter-defibrillator, with anemia (haemoglobin <100 g/L) at admission, who underwent cardiothoracic surgery or had a history of moderate or high degree valvular pathology, who had life-expectancy of less than 1 year and who did not sign informed consent. Patients were admitted through the Emergency Department, where they were evaluated for onset and duration of pain, co-morbidities and risk factors. Vital signs and complete physical status were recorded. All patients underwent 12-lead ECG and patients with acute STEMI were taken immediately to the catheterization laboratory for primary PCI.

All patients who met the inclusion criteria were randomized into two groups by means of sealed envelopes.

Inclusion Criteria:

• Acute myocardial infarction with ST elevation
• Less than 12 hours of symptoms beginning
• Clear indication for primary PCI
• No contraindication for primary PCI
• Age 18 to 85

Exclusion Criteria:

• Cardiogenic or any other shock
• More than two culprit lesions/vessels
• Any major complication during PCI
• Unsuccessful intervention

Only complete study data of all 100 patients recruited so far, will be shared if needed