Reperfusion therapy in acute myocardial infarction saves viable myocardium, but paradoxically reestablishment of coronary artery flow also induces damage and cell death, decreasing the full benefit of reperfusion in terms of reduction of infarct size and preservation of ventricular function . Myocardial reperfusion can in itself produce more damage and cell death, this process defines the phenomenon of reperfusion injury, which could be prevented by applying additional therapies.

During myocardial ischemia, due to lack of O2, the myocyte leaves energy production from the aerobic metabolism of lipids and the production of energy in the form of phosphates will depend, in this situation, on the anaerobic metabolism of glucose. As a result they are consumed muscle glycogen stores that produce little ATP, and also generating acidosis. The cell membrane loses its ability to maintain the fluid's electrolyte balance. Cellular edema is generated by the entry of sodium and water, leading to cell rupture. During ischemia and reperfusion free radicals are produced that stimulate inflammation and consequently release prothrombotic and cytotoxic substances that also produce cellular damage. Due to its osmotic, antithrombotic, anti-inflammatory and rheological effects, dextran could be useful in this scenario.

The administration of a solution in the distal bed, for the protection of the myocardium, before opening the epicardial artery is called by us "controlled reperfusion". The researchers think, using a solution with venous blood, containing less O2 but retaining buffer properties; enriched with Dextran, which has onctic power, anti-inflammatory and anticoagulant properties, and molecules similar to glucose; results in a potentially useful solution for myocardial protection in this scenario.

The group of investigators expect that controlled reperfusion treatment will reduce the incidence of ST correction and infarct size by 20-30%, improving the prognosis in terms of mortality and heart failure.

Inclusion Criteria:

• Women and men over 18 years of age
• First acute myocardial infarction with ST elevation, within 6 hours of the initial symptoms, that are admitted for primary PCI at the Hospital San Bernardo.
• TIMI 0 or 1 flow in the culprit artery.

Exclusion Criteria:

• Not able or willing to give informed consent.
• Participate in another protocol.
• Pregnancy.
• History of any of the diseases listed: cardiomyopathy, valvular disease severe, any disease with a life expectancy of less than 1 year.
• Contraindication for protocol drugs (Dextran).
• LBBB or pacemaker.
• Prolonged cardiopulmonary resuscitation.
• Cardiogenic shock.
• Left main coronary lesion or culprit lesion in venous graft.
• Large artery not feasible for PCI, guilty vessel of small caliber or very distal lesion.