Incidence of Long-TeRm Atrial Fibrillation After Acute Illness

Inclusion Criteria: 1. Patient has an existing clinical indication for implantation of an insertable cardiac monitor (ICM) and will undergo ICM implantation as part of their standard medical care. 2. Patient is scheduled to receive or has received a Boston Scientific LUX-DX™ insertable cardiac monitor. 3. Episode of acute AF. Acute AF is defined as AF detected in an acute care setting or during an acute illness. Before enrollment, the following tests are minimally required as standard tests to establish the diagnosis of acute AF: * 12-lead ECG for AF detection * 24-h ECG or telemetry monitoring for AF detection and PAC analysis 4. Patient or legally authorized representative signs and dates the patient consent form. 5. Patient is ≥18 years old. 6. Patient is willing and able to comply with all study procedures and attend the required follow-up visits for the duration of the study. Exclusion Criteria: 1. Patient has a known history of AF or atrial flutter prior to the index acute AF episode. 2. Patient has another indication for antiarrhythmic medications according to AHA/ACC/HRS guidelines, independent of the acute AF episode. 3. Patient has a permanent contraindication to oral anticoagulation (OAC) that, in the opinion of the treating physician, would preclude any future consideration of OAC for AF management. 4. Patient is currently enrolled in another clinical trial that will affect the objectives or endpoints of this study. 5. Patient's life expectancy is less than one year, as determined by the treating physician. 6. Patient is pregnant. 7. Patient has a current indication for implant with a cardiac implantable electronic device (CIED) such as a pacemaker or defibrillator, or an implantable hemodynamic monitoring system, as the study intervention would be redundant or potentially interfere with the clinical indication. 8. Patient is not fit, able, or willing to follow the required procedures of the Clinical Investigation Plan.