After a myocardial infarction (MI), patients discharged home in sinus rhythm may develop AF that is asymptomatic, undetected, and undertreated. Previous studies (CARISMA and ARREST) have demonstrate high rates of new-onset AF recorded on implantable loop recorder (ILR), although the routine implantation of ILRs post-MI remains costly and invasive. The external loop recorder may effectively identify patients with new-onset AF through a validated diagnostic algorithm and targeted monitoring during a high-risk period (immediately after hospital discharge). We will prospectively randomize patients to receive an external loop recorder or standard care, evaluating rates of new-onset AF developing within 30 days after MI.

The SIMPL-AF trial will evaluate the role of intensive monitoring after myocardial infarction, assessing for new-onset AF after hospital discharge. Patients will be randomized to receive intensive monitoring or standard care in a 2:1 distribution. Patients randomized to intensive monitoring will receive a SpiderFlash® monitor, worn for 30-days after discharge and returned for analysis.

The primary objective of this study is to evaluate at the incidence of new-onset AF at 30-days post-MI using an intensive monitoring strategy, compared to standard of care. Secondary objectives include the impact of intensive monitoring on oral anticoagulation rates at 90-days and 1-year after monitoring, and the risk factors for developing new-onset AF, and the variables associated with initiating or withholding anticoagulation.

Inclusion Criteria:

• Patients with ST-elevation myocardial infarction (STEMI) or Non-ST-elevation myocardial infarction (NSTEMI; Third Universal Definition of MI) with or without PCI. All patients must have troponin elevation.
• No history of AF during hospitalization, at discharge, or pre-existing AF documented on history (i.e. hospital records, previous hospitalization, ECG records).
• No anticoagulation for AF or other indications (i.e. LV thrombus, heart valves, venous thromboembolism/deep venous thrombosis).
• No concomitant disease expected to reduce expected lifespan to <2 yrs.

Exclusion Criteria:

• Patients receiving CABG surgery during this hospitalization or planned cardiac surgery within the next 3 months.
• Patients with spontaneous coronary artery dissection (SCAD), non-atherosclerotic coronary disease (NACAD), and Takotsubo cardiomyopathy are excluded from this study.
• Patients with contraindications to anticoagulation.
• Patients with a chronic skin disorder on the upper torso, or an allergy to medical tape or glue.