Patients with diabetes mellitus have higher short-term and long-term mortality rates after acute myocardial infarction (MI) than do patients without diabetes, even in the era of thrombolytic therapy. Diabetes is also an independent predictor of mortality following other acute coronary syndromes (ACS), such as unstable angina or non-Q-wave MI. Even in patients without a previous diagnosis of diabetes, hyperglycemia on admission for an acute MI is associated with higher mortality. These cases may represent previously unrecognized diabetes or glucose intolerance.
Insulin therapy in patients with diabetes presenting with an acute MI has been shown to be beneficial. The Diabetes Mellitus Insulin Glucose Infusion in Acute Myocardial Infarction (DIGAMI) study compared the use of conventional therapy to an insulin-glucose infusion to maintain blood glucose (BG) levels between 7.0 and 10.0 mmol/L, followed by multidose subcutaneous (SC) insulin (intensive insulin therapy). Intensive insulin therapy resulted in almost a 30% reduction in long-term mortality rate out to 3.4 years. One life was saved for every nine patients treated with intensive insulin therapy. Particular benefit was observed in patients who had fewer cardiovascular risk factors and those who were not using insulin before randomization. An unresolved issue under investigation is whether the reduction in long-term mortality observed in the intensive insulin therapy group was due to the acute effect of insulin treatment on the myocardium, the use of SC insulin after the MI or improved glycemic control after the MI. Given the magnitude of benefit seen in the DIGAMI study and the knowledge that diabetes is a predictor of mortality rates after ACS, use of an insulin-glucose infusion to improve glycemic control in acute situations may be beneficial for all patients with diabetes presenting with ACS. Patients who are treated with a multidose insulin regimen after an MI should be followed closely by a diabetes health care team with experience in managing intensified insulin control.
All patients with acute MI, regardless of whether or not they have a prior diagnosis of diabetes, should have their BG level measured on admission [Grade D, Consensus], and those with BG over 12.0 mmol/L should receive insulin-glucose infusion therapy to maintain BG between 7.0 and 10.0 mmol/L for at least 24 hours, followed by multidose SC insulin for at least three months [Grade A, Level 1A]. An appropriate protocol should be developed and staff trained to ensure the safe and effective implementation of this therapy and to minimize the likelihood of hypoglycemia [Grade D, Consensus].
Reference:
1. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2003 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada. Peri-acute Coronary Syndrome Glycemic Control. Can J Diab 2003;27(suppl 2):S115-6.