Patients with heart attacks caused by blocked coronary arteries are usually treated with a technique called primary angioplasty. Although this treatment is very successful it can result in damage to the heart muscle when the artery is opened due to reperfusion injury. Cooling the entire body has been shown to reduce heart muscle damage during heart attacks in some patients but not in others, however it is uncomfortable due to the shivering, expensive and can result in delays in opening the blocked artery. We are investigating a simpler way to cool the heart muscle directly using cooled fluid passed through the catheter without the shortcomings of entire body cooling. This pilot will address safety and feasibility considerations.

The precise mechanisms involved in ischaemia/reperfusion injury is not fully understood but a number of factors are thought to contribute to cardiac dysfunction14, 15. These include : 1. reperfusion arrhythmias; 2. microvascular obstruction or no-reflow phenomenon; 3. myocardial stunning and 4. cardiomyocyte apoptosis. It is estimated that ischaemia/reperfusion injury occurs in > 30% of patients and is associated with reduced myocardial salvage and poor prognosis16-18. Ischaemia/reperfusion injury may account for up to 50% of the final infarct size9.

Deep hypothermia (< 30 °C) has long been used in protecting the heart during coronary artery bypass grafting and heart transplantation. Intermittent antegrade or retrograde infusion of cold cardioplegia appears to reduce myocardial ischaemia and improves outcome19, 20. Deep hypothermia however can cause spontaneous ventricular fibrillation and impaired cardiac function and its application is limited to the unconscious patient.

Inclusion Criteria:

• Men and women aged between 18 and 80 years presenting with ischaemic chest pain of <6 hours and STsegment elevation on the ECG of >0.2 mV in 2 contiguous leads.

Exclusion Criteria:

• Patients with cardiac arrest, previous AMI or CABG, known congestive heart failure, endstage kidney disease or hepatic failure, recent stroke, coagulopathy, pregnancy, or cardiogenic shock.
• Patients who are unable or unwilling to provide assent and informed consent.