A heart attack (myocardial infarction) occurs when an artery supplying blood to the heart is suddenly blocked resulting in damage to the heart muscle. Patients presenting to hospital with a heart attack undergo an immediate angiogram (x-ray of the arteries in the heart) and are usually treated immediately with a balloon and stent to open their blocked artery. This procedure is called primary percutaneous coronary intervention (or primary PCI for short). An angiogram is a routine procedure that involves insertion of fine plastic tube (catheter) into either the groin or wrist under local anaesthetic. The tube is passed into the artery in the heart and X-ray pictures are taken to find out if the arteries are blocked. Blocked arteries can usually be opened by passing a small balloon into the artery, via the fine plastic tube followed by placement of a stent (a fine metal coil) into the artery to prevent it from blocking again. Although this treatment is very successful, it can result in damage to the heart muscle when the artery is opened. 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. The investigators are conducting a series of research studies to find out if cooling the heart muscle directly through the catheter being used for the normal primary angioplasty treatment using room temperature may be effective in preserving heart muscle, without the shortcomings of entire body cooling. The investigators have already published an initial series of ten cases in which this treatment appeared to be feasible without causing significant clinical problems. The present study is a pilot study designed to assess the rate of patient recruitment and feasibility of this new treatment while exploring some detailed outcomes measuring the restoration of blood flow within the coronary artery at the end of the procedure. Ultimately if the present pilot study is successful, the investigators plan to go on to undertake a much larger randomised outcome study to determine definitively whether this treatment can help reduce heart attack size.