Long-term Beta-blocker Therapy After Acute Myocardial Infarction

Inclusion Criteria: * Subject must be at least 19 years of age. * Subject who have been continuing β-blocker therapy for at least 1 year after acute myocardial infarction regardless of the time of diagnosis * Subject is able to verbally confirm understandings of risks and benefits of this trial, and he/she or his/her legally authorized representative provides written informed consent prior to any study related procedure. Exclusion Criteria: * Subject whose left ventricle ejection fraction was less than 40% from echocardiography performed after acute myocardial infarction or who have never received echocardiography. * Treatment history of heart failure * Contraindication to β-blocker therapy (history of symptomatic bronchial asthma or chronic obstructive pulmonary disease, 2nd or 3rd degree AV block, cardiac pacemaker implantation, or other cases where β-blocker cannot be used under the judgment of the clinician) * Non-cardiac co-morbid conditions are present with life expectancy \<1 year or that may result in protocol non-compliance (per site investigator's medical judgment). * History of atrial fibrillation * Pregnancy or breast feeding