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).