Association between blood glucose level and in-hospital mortality in patients with acute myocardial infarction

Abstract

Dear Editor, Diabetes mellitus increases cardiovascular-related morbidity and mortality and high blood glucose even before it reaches the threshold to diagnose diabetes is associated with higher cardiovascular risk. Several studies previously reported that adverse cardiac events increased in patients with acute myocardial infarction. However, the association between admission blood glucose level and cardiac-related mortality and morbidity was not studied in Iranian population. Therefore, we conducted a study to assess the association between on admission blood glucose level and in-hospital cardiac mortality and prognosis in these patients. The study designed prospectively and performed on patients presenting to the emergency department of our center with acute ST elevation myocardial infarction (STEMI) between April, 2008 and April, 2010. STEMI was diagnosed based on the acute rise and gradual fall of cardiac enzymes with ischemic symptoms and ECG changes (ST segment elevation or new left bundle branch block). Exclusion criteria were severe co-morbidities, history of valvular heart disease, and low ejection fraction before infarction (EF<35%). Demographic characteristics of all patients collected initially. Patients were divided into four groups according to their blood glucose levels (first group [G1]: <140 mg/dL; second group [G2]: 140–199 mg/dL; third group [G3]: 200–249 mg/dL; forth group [G4]: ≥250 mg/dL). Primary endpoint of our study was in-hospital mortality. Secondary endpoint defined as in-hospital cardiac and non-cardiac morbidities included cardiogenic shock, atrio ventricular block, left ventricular clot formation, and cardiac arrhythmias. In-hospital non-cardiac morbidities were defined as cerebrovascular events, renal failure, and gastrointestinal bleeding. Follow-up data were collected at discharge or demise time. Out of 396 patients enrolled in this study, 78% were male with mean age of 58 ± 12. There was significant increase in on-admission blood glucose level when patients had history of diabetes mellitus or smoking (p < 0.001). Mortality in G1 group was lower compared to other groups and G4 had highest mortality (p = 0.001). Cardiac and non-cardiac morbidities were 18% in G1 comparing to 22.8% in G4 which was not significant. The association between clinical characteristics of patients and in-hospital mortality assessed with multivariate analysis. There was higher in-hospital mortality in female patient group (p < 0.003; OR = 2.56; CI 95%, 1.34–4.85) and hypertensive patients (p < 0.002; OR = 2.63; CI 95%, 1.39–4.99). Patients received coronary intervention as treatment had significantly lower mortality compare to patient received only medical treatment. After binary logistic regression adjustment for confounding variables only the blood glucose level and age were still the independent predictor of in-hospital mortality (p = 0.002) and adjusted odds ratio for blood glucose level was 1.56 (CI 95%, 1.18–2.07) in the forth quartile compared with the first quartile. Age as an independent predictor of in-hospital mortality had adjusted odds ratio of 1.05 (CI 95%, 1.02–1.08) (p = 0.001). Cardiovascular mortality rate is out standing in developing countries and age-related mortality rate of CADs is reached up to 40% in Iran.1 There are limited data on CAD prevalence and CAD risk factors in Middle East. Previous study proved that diabetes is the most powerful risk factor for CAD.2 Hyperglycemia is associated with larger infarct size, lower LVEF, and poor prognosis. Moreover, high glucose level has important role in short- and long-term prognoses of AMI patients. The present study shows that patients with STEMI and hyperglycemia on admission have a higher risk of in-hospital mortality and this relation is independent of previous diabetes history.