New-Onset Atrial Fibrillation Complicating Acute Myocardial Infarction in ShangHai

Inclusion Criteria: * Patients hospitalized for acute MI between February 2014 and March 2018 in the CCU department of Shanghai Tenth People's Hospital; * Adult patients (\>18 years old). Exclusion Criteria: * Patients with a medical history of pre-existing AF; * Patietns with a medical histroy of Rheumatic valvular disease; * Patietns with a medical histroy of sick sinus syndrome; * Patients undergoing emergent coronary artery bypass surgery; * Patients' medical records with serious deficiencies and critical information (e.g. demographic data, laboratory testings, etc.) cannot be retrieved; * Patients who refused to receive electronic monitoring during hospitalization and the data of cardiac rhythm cannot be obtained; * Premature discharge due to nonmedical reasons such as nonpayment, failure to comply with program rules, conflicting with treatment staff, etc.