Hyperglycemia and myocardial infarction

Increased blood glucose concentration (hyperglycemia) is an essential diagnostic feature of diabetes, and normalization of blood glucose is the principal aim of diabetes treatment. Hyperglycemia can also occur in the non-diabetic population when normal hormonal control of blood glucose concentration is disturbed by the stress associated with acute/critical illness. 

One such acute illness is myocardial infarction. Irrespective of diabetes status it is quite common for blood glucose to be raised in the immediate period following acute myocardial infarction (AMI). In a recently published review the author discusses the current understanding of the significance of hyperglycemia occurring as a result of AMI for both diabetic and non-diabetic patients. 

A significant part of the review is devoted to the discussion of the large body of epidemiological evidence that confirms an association between hyperglycemia and mortality following myocardial infarction. There is an inverse linear relationship between admission glucose concentration and chance of surviving to hospital discharge following myocardial infarction. 

In one study in-hospital mortality was just 2 % among those with blood glucose <5.0 mmol/L, 5 % among those with blood glucose 7.0-9.0 mmol/L and 18 % among those with blood glucose >13.0 mmol/L. 

Recent research suggests that for diabetic patients the relationship between admission blood glucose and mortality is U-shaped rather than linear, so that admission blood glucose in the range of 9.0-10.0 mmol/L is associated with the lowest mortality (2 %), whereas both blood glucose around 6.0 mmol/L (low) and blood glucose around 15.0 mmol/L (high) are associated with equally high mortality (13 %). 

It remains unclear if the undisputed association between hyperglycemia and increased mortality following AMI is causative, but the author of this study reviews a range of experimental and clinical studies that have demonstrated several mechanisms by which hyperglycemia could adversely affect outcome of myocardial infarction. 

The final part of the review is devoted to a discussion of clinical studies examining if treatment aimed at normalizing blood glucose improves outcome of AMI patients who present with hyperglycemia.