The purpose of this study is to test the impact of pharmacological myocardial metabolic support, in the form of intravenous (IV) glucose, insulin and potassium (GIK), for the treatment of patients with threatened or established acute myocardial infarction (AMI). Patients with symptoms consistent with acute coronary syndromes (ACS), considered to be having a threatened or established AMI will be identified by emergency medical system (EMS) paramedics in the field during transport to the receiving hospital. Qualified patients must be 30 years of age or older and have a 12-lead electrocardiogram (ECG) with at least one of the following: ACI-TIPI score of 75% or more and/or Thrombolytic Predictive Instrument mortality scores printed (or if neither of the previously described are present, but the ECG shows a definitive acute MI with ST segment elevation). To assist paramedics, the ECGs will be equipped with two cardiac predictive instruments: the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI) and the thrombolytic predictive instrument (TPI). Patients who have end stage renal failure requiring dialysis, who are hemodynamically unstable, or who have clinically significant heart failure (HF) (Killip Classes 3 or 4) will be excluded.

For patients who meet the inclusion/exclusion criteria, the study drug solution will be given while en route in the ambulance. They will be randomized to receive a 12-hour IV infusion of either GIK or placebo. The intervention GIK solution will consist of 1 liter of 30% dextrose mixed with 80 mEq of potassium chloride, and 50 units of regular insulin. The placebo IV bags will appear identical to the GIK solution bags. They will contain 5% dextrose in each bag. Infusion bag labels will contain a study drug specific number (randomization number) that can be reconciled with the randomization scheme.

Paramedics caring for the patient will confer with the ED attending physician upon arrival to the hospital and inform them of the patient inclusion into the IMMEDIATE Trial who will then oversee the continuation of the study drug solution. He/she will then work with the nursing staff to facilitate the transfer of the study solution from the paramedic to the ED staff, at which point the 1 liter solution will be placed on an IV pump according to study protocol. Glucose and potassium levels will be checked upon ED arrival, 6 and 12 hours after the start of the study drug. Treatment of abnormal values and subsequent testing will be at the discretion of the treating physician. It will also be left up to the discretion of the treating physician to stop the infusion prematurely if deemed clinically warranted.