The purpose of this study is to determine the incidence of paroxysmal atrial fibrillation (AF) in ischemic stroke patients who have a presumed known stroke etiology other than atrial fibrillation.

Recent studies suggest that their is a relatively high incidence of silent paroxysmal atrial fibrillation (PAF) in cryptogenic ischemic stroke patients. Detection of silent PAF in this population, however, requires prolonged cardiac monitoring. On the other hand, there is no understanding of the frequency of silent PAF in patients with a "known" or presumed etiology for their ischemic stroke other than AF. If this incidence is also found to be significant, a dramatic change in stroke evaluation and management would likely occur. This study intends to find the incidence of PAF in a population of recent (within 7 days) ischemic stroke patients (or MRI positive "transient ischemic attack (TIA)" patients) who have presumed etiology for their stroke other than atrial fibrillation or other high risk cardiac lesion. Stroke etiology will be determined through a standard post-stroke evaluation that includes:

• Brain MRI
• 12-lead electrocardiogram (ECG) for AF detection
• 24-h ECG monitoring for AF detection (eg, Holter monitor or cardiac telemetry)
• Transthoracic and/or Transesophageal echocardiogram
• CT or MR angiography of the head and neck
• Hypercoagulable blood panel for patients less than 55 years-old. Preliminary hypercoagulable work-up within 7 days will include the antiphospholipid antibody syndrome results, which will be needed to determine stroke management. All other results, which could take longer to return, including genetic tests of hypercoagulability, rarely change stroke management.

To find occult PAF in this population, participants will have an insertable cardiac monitor (Reveal LINQ ICM) implanted within 7 days of the incident stroke and will be monitored for at least 1 year.

Inclusion Criteria:

• Patients with a recent ischemic stroke or transient ischemic attack (TIA) with brain infarction on brain imaging.
• No history of atrial fibrillation or finding of atrial fibrillation on standard inpatient monitoring (electrocardiogram, telemetry, 24-hour Holter monitor)
• Have a presumed stroke etiology: Lacunar or small vessel thrombosis, extra-cranial or intracranial atherosclerotic stenosis or dissection, arteriopathy or vasculitis, hypercoagulable state, aortic arch plaque with or without mobile elements, or evidence of a low-risk cardiac source (e.g., patent foramen ovale with or without atrial septal aneurysm and with or without evidence of venous thromboembolic source).
• Have virtual CHADS2 score ≥3 or
• Have 2 or more of the following co-morbidities: obstructive sleep apnea, coronary artery disease, (Chronic Pulmonary Obstructive Disease (COPD), hyperthyroidism, Body Mass Index> 30, prior myocardial infarction, prolonged PR interval (>175 ms) or renal impairment (GFR 30-60).
• Patient or legally authorized representative who is willing to sign written consent form.
• Patient is ≥40 years old (patients younger than 40 years old have a very low likelihood of having atrial fibrillation and are therefore excluded from the study).
• Patient can have the device implanted within 7 days of the incident ischemic event

Exclusion Criteria:

• Documented history of AF or atrial flutter.
• Evidence of a high-risk cardiac source of embolism (Left Ventricular or Left Atrial thrombus or "smoke," emboligenic valvular lesion or tumor)
• Untreated hyperthyroidism.
• Myocardial infarction or coronary bypass grafting within 1 month prior to the stroke/TIA.
• Valvular disease requiring immediate surgical intervention.
• Permanent indication for anticoagulation at enrollment.
• Permanent oral anticoagulation contraindication.
• Already included in another clinical trial that will affect the objectives of this study.
• Life expectancy is less than 1 year.
• Pregnancy. Urine or serum pregnancy test is required for women of child bearing potential to exclude pregnancy.
• Patient is indicated for implant with a pacemaker, implantable cardioverter-defibrillator, CRT device, or an implantable hemodynamic monitoring system
• Patient is not fit, or is unable or unwilling to follow the required procedures of the Clinical Investigation Plan.
• Cryptogenic Stroke: A stroke/TIA will be considered cryptogenic if no cause is determined despite extensive inpatient workup according to the standard diagnostic protocol at North Shore University Hospital.

3 years

Relatively small sample size limits our study's power to detect and confirm all factors associated with PAF detection. The number of non-PAF patients lost to follow-up by 6 and 12 months that may have resulted in an underestimation of PAF burden.