Methods:
This study was approved by Lifespan Institutional Review Board. Informed consent was waived as this is a retrospective study.
The study population included all patients presenting to a comprehensive regional stroke center with a primary diagnosis of ischemic stroke between January 2016 and June 2017. All patients enrolled in the stroke database underwent standard ischemic stroke evaluation including laboratory testing, neuroimaging, 12-lead EKG, transthoracic echocardiography (TTE), and cardiac telemetry monitoring for at least 24 hours. The stroke subtype was assigned by a vascular neurologist, who was following the patients over the course of index hospitalization, based on the TOAST criteria20 and ESUS subtype was defined based on the ESUS consensus criteria21. This data was extracted by chart review. Stroke subtype was divided into two categories: ESUS and NCE. Demographic variables, vascular risk factors, and laboratory covariates (age, sex, history of hypertension, diabetes mellitus, hyperlipidemia, coronary artery disease, congestive heart failure, renal disease, systolic blood pressure, smoking status, National Institutes of Health Stroke Scale (NIHSS) score) were also extracted and collected on the Research Electronic Data Capture database (REDCap; Vanderbilt University, Nashville, TN). All ESUS patients were given a prescription of cardiac event monitor (CEM) as per guidelines regardless of symptoms. Those with negative CEM results were given implantable loop recorders (ILR). The presence of AF was defined as identification of AF for more than 30 seconds on monitoring.
Patients with a history of atrial fibrillation or any of the following conditions were excluded: moderate to severe valve disease (as determined by clinical echocardiography reports), a left ventricular ejection fraction (LVEF) of less than 40%, pericardial effusion causing tamponade, any type of congenital heart disease, a prosthetic heart valve, left ventricular assist device, or poor image quality (LA chamber foreshortening, or unclear atrial walls etc.) to perform STE analysis (Figure 1).