Predictive factors of major adverse cardiac events and clinical outcomes of acute myocardial infarction in young Korean patients

Background and Objectives: Acute myocardial infarction (AMI) occurring in patients at a young age (40 years or younger) is an uncommon condition and is characterized by multiple cardiovascular risk factors. We analyzed the risk factors of young-aged Korean AMI patients (age of 40 years or younger) and other AMI patients, who were registered in the Korea Acute Myocardial Infarction Registry (KAMIR) for one year. Subjects and Methods: In 2006, 8,565 patients (mean age 64.4±12.7 years; 5,591 males) were registered in the KAMIR. The patients were divided into two groups: Group I (younger patients ≤40 years; n=261; mean age 35.9±4.5 years; 245 males) and Group II (older patients >40 years; n=8,304, mean age 65.4±11.8 years; 5,330 males). The clinical and angiographic characteristics and major adverse cardiac events (MACE) were compared for the two groups of patients. Results: The baseline clinical characteristics of gender, age, risk factors (hypertension, smoking, diabetes, familial history) and body weight were different between the two groups (p<0.001). The baseline echocardiographic and laboratory findings of the initial ejection fraction, and the glomerular filtration rate, level of creatine kinase (CK), level of CK-MB isoenzyme, total cholesterol level, triglyceride level, and N-terminal prohormone brain natriuretic peptide (NT-proBNP) level were different between the two groups (p≤0.001). According to the use of multiple logistic regression analysis, use of thrombolysis [p=0.009, adjusted hazard ratio (aHR)=9.140, 95% confidence interval (CI): 1.727-48.383], a high blood glucose level (p=0.029, aHR=1.008, 95% CI: 1.001-1.016), a low body mass index (<25 kg/m², p=0.031, aHR=6.236, 95% CI: 1.183-32.857), and a high CK-MB level and high Thrombolysis in Myocardial Infarction (TIMI) risk score were independent predictors of MACE at 1 year after an AMI in young age patients. Early clinical outcomes were better in Group I than in Group II patients, but one-, six- and twelve-month MACE were not different between the two groups. Conclusion: The independent predictors of MACE at 1 year in young age AMI patients were the use of thrombolysis, a high blood glucose level, a low body mass index, a high CK-MB level and a high TIMI risk score. Patients that have had an acute myocardial infarction at a young age have a better early clinical outcome, but the long-term clinical outcomes were not different compared with older patients, and thus long-term intensive medical therapy will be required, even in young AMI patients.