To investigate the prognostic impacts of the atrial fibrillation burden (AFb) in acute myocardial infarction (AMI) patients who developed paroxysmal new-onset atrial fibrillation (NOAF) during the index AMI hospitalization.

In the present study, investigators retrospectively reviewed the medical records of all acute MI patients who were admitted to the coronary artery unit (CCU) of Shanghai Tenth People's Hospital, KaiFeng Central Hospital, and the First Affiliated Hospital of Zhengzhou University between January 2014 and January 2022. All patients will routinely receive continuous electronic monitoring (CEM) throughout their hospital stay to detect cardiac arrhythmias including the AF events. Of these, patients with AMI without a history of AF who developed a first documented AF episode will be considered for inclusion. The AFb is measured as a percentage (%) by dividing the total AF duration by the total CEM duration.

Inclusion Criteria:

1. Patients hospitalized for AMI including both STEMI and NSTEMI between January 2014 and January 2022 at the CCU department of Shanghai Tenth People's Hospital, KaiFeng Central Hospital, and the First Affiliated Hospital of Zhengzhou University.
2. Patients who developed a first documented AF (NOAF) during the index AMI hospitalization；
3. Adult patients (>18 years old).

Exclusion Criteria:

1. Patients with a medical history of pre-existing AF;
2. Patients with a medical history of rheumatic valvular disease;
3. Patients with a medical history of sick sinus syndrome;
4. Patients undergoing emergent coronary artery bypass surgery;
5. Patients' medical records with serious deficiencies and CEM data cannot be retrieved;

Patients with post-MI NOAF