Inclusion Criteria:
1. Consecutive adult patients (18 yrs of age or older) diagnosed with cryptogenic stroke despite complete neurodiagnostic workup, including the following:
A. Transthoracic echocardiogram B. EKG and 24h minimum cardiac telemetry C. Cervical and intracranial vessel imaging D. No known and established source of cerebral embolism after completion of the aforementioned testing E. CT or MRI evidence of acute cerebral infarction F. Onset of stroke or last known well within 2 weeks of hospitalization or study inclusion start date (unless time last known well is unknown)
2. Left ventricular ejection fraction greater than or equal to 20%
Exclusion Criteria:
1. Patients with an established stroke mechanism that is diagnosed prior to or at the time of the index stroke event. Examples include but are not limited to:
A. New diagnosis of atrial fibrillation during index stroke admission, or history of prior atrial fibrillation B. Cervical or intracranial atherosclerosis in a vessel supplying the infarcted brain region, with 50% luminal stenosis by NASCET criteria C. Cervical or intracranial arterial dissection D. Inflammatory vasculopathy (e.g., giant cell arteritis, primary central nervous system angiitis) E. Acute myocardial infarction or cardiac arrest at the time of stroke F. Intracardiac thrombus (e.g., left ventricular, left atrial, left atrial appendage thrombus), irrespective of cardiac function G. Small vessel disease (defined by the presence of a single, subcortical infarction less than 1.5cm in diameter on computed tomography, less than 2.0cm in diameter on diffusion-weighted imaging, or without radiographic evidence of infarction BUT with symptoms consistent with a subcortical syndrome-e.g., pure motor hemiparesis, pure hemisensory impairment, mixed motor-sensory syndrome, ataxic hemiparesis, or dysarthria-clumsy hand syndrome)
2. Patients without follow-up information at 30 days (although patients who expired within 90 days of stroke are still eligible for inclusion)
3. Patients enrolled in a randomized clinical trial in which antithrombotic group is blinded to the investigator
4. Transient ischemic attack
5. Primary intracerebral hemorrhage
