Elevated blood glucose levels on admission to hospital has previously been shown to be an independent predictor of mortality in patients presenting with ST-segment elevation myocardial infarction (STEMI). Limited data is available on whether this is the case for both diabetic and non-diabetic patients. Cardiogenic shock is a serious complication of STEMI and has a high mortality rate. These patients may have even higher blood glucose due to higher levels of gluconeogenesis in response to acute stress. New research published in Critical Care has found that elevated admission blood glucose is associated with a higher 30-day mortality rate in non-diabetic patients presenting with STEMI complicated by cardiogenic shock, but not in diabetic patients.
A team of researchers, led by Hyeon-Cheol Gwon of Sungkyunkwan University School of Medicine, South Korea, collected clinical and laboratory data (including admission blood glucose and 30-day mortality) from a large multicentre prospective Korean registry. Cumulative 30-day mortality was calculated after stratifying by admission blood glucose and the presence or absence of diabetes. 30-day mortality increased as admission blood glucose increased. When looking at all patients, 30 day mortality was 20.4 percent for those with an admission blood glucose of less than 7.8-10.9 mmol/L, compared to 43.7 percent for those with blood glucose of 16.6 mmol/L or greater. The same increase in mortality was seen when looking at non-diabetic patients; but for diabetic patients there was no significant difference.
The association between admission hyperglycaemia and increased mortality is thought to be due to complex interplay between regulatory hormones including cortisol, glucagon, growth hormone and cytokines. The findings of this and other studies suggest that the toxic effects of hyperglycaemia during short term illness may be less in diabetic patients. One explanation for this is that diabetic patients are likely to have received insulin or oral anti-glycaemic agents before being admitted, which may mitigate the toxic effects of stress hyperglycaemia. An alternative explanation is that patients with diabetes may develop resistance to hyperglycaemia. A moderate or severe degree of hyperglycaemia or variability in blood glucose which may have a toxic effect in a patient without diabetes, may therefore be better tolerated in a patient with diabetes.
Identifying high risk patients with STEMI complicated by cardiogenic shock is challenging, and tools including the GRACE and TIMI risk scores have been developed to this end. The researchers found that adding admission blood glucose to these scores increased their predictive values for non-diabetic patients but not diabetic patients. These results may therefore be useful in developing a new risk model in cardiogenic shock and improve bedside risk stratification. Further research is needed to determine whether therapies to lower blood glucose would be beneficial in reducing mortality in the context of STEMI with cardiogenic shock.