Prognostic impact of hyperglycemia in nondiabetic and diabetic patients with ST-elevation myocardial infarction: Insights from contrast-enhanced magnetic resonance imaging

Background - Hyperglycemia on admission is associated with increased mortality rates in patients with ST-elevation myocardial infarction (STEMI). However, data regarding the relationship between hyperglycemia and myocardial damage in STEMI are scarce. The aim of this study was to determine the relationship of diabetes mellitus status and hyperglycemia on myocardial damage assessed by cardiovascular magnetic resonance imaging and to evaluate the long-term prognostic significance of hyperglycemia in a high-risk STEMI population. Methods and Results - Glucose levels were determined on admission in 411 consecutive STEMI patients reperfused by primary angioplasty. Patients were categorized on the basis of diabetes mellitus status and admission glucose level. Magnetic resonance imaging was performed for assessment of infarct size and microvascular obstruction. The primary clinical end point was the occurrence of major adverse cardiovascular events at long-term follow-up. STEMI patients with pre-existing diabetes mellitus were at greater risk for major adverse cardiovascular events (32% versus 11%; P<0.001) despite having similar infarct sizes and extent of reperfusion injury than nondiabetic patients. Glycemic status on admission was associated with greater myocardial damage and an increased risk for major adverse cardiovascular events (P<0.001). In nondiabetic patients, the risk of severe myocardial injury started to rise once admission glucose exceeded 7.8 mmol/L, whereas the threshold was higher among patients with diabetes mellitus (>11.1 mmol/L). Conclusions - The higher mortality rate in diabetic versus nondiabetic STEMI patients is not explained by more pronounced myocardial damage. Hyperglycemia on admission is associated with greater myocardial injury and an increased risk of major adverse cardiovascular events at long-term follow-up. However, hyperglycemia has a stronger relationship to myocardial injury in nondiabetic compared with diabetic patients.