Introduction:
Ischemic stroke accounts for 87% of all strokes1, and cryptogenic stroke constitutes approximately 30-40% of all ischemic strokes2, 3{Perera, 2022 #584}. Embolic Stroke of Undetermined Source (ESUS) is a subtype of cryptogenic stroke in which there is embolic-appearing infarction on CT and/or MRI without an identifiable etiology despite standard diagnostic evaluation4. It is associated with a high recurrence5, 6; thus, in addition to risk factor modification, identifying and targeting the primary causal mechanisms may improve secondary prevention strategies7. Better characterization of left atrial (LA) structure and function may elucidate a mechanistic pathway in the development of cryptogenic stroke. Previous studies have shown an association of left atrial enlargement (LAE)8, 9 and left atrial volume index (LAVI)10 with ESUS stroke subtype as compared to non-cardioembolic (NCE) stroke subtype. However, LA chamber remodeling and biomechanical dysfunction precede volumetric changes in LA chamber11. Speckle tracking echocardiography (STE) and strain analysis have been shown to detect these early signals prior to structural changes found on traditional imaging methods12-14. Atrial cardiopathy has been characterized as a time-dependent adaptive structural remodeling with electrical and mechanical dysfunction causing stasis of blood. It may provide a potential substrate for the development of thrombus even in the absence of atrial enlargement or fibrillation13, 15. Atrial fibrosis, an early sign of atrial remodeling, correlates inversely with LA strain16, 17 and is reported more frequently in ESUS compared NCE subtype18. A recent single-center study showed the association of LA strain and stroke subtypes including cryptogenic stroke19.
The goal of our study is to investigate the relationship between LA strain and stroke, specifically ESUS and NCE stroke subtypes, in a geographically distinct population using a comprehensive stroke database. Additionally, we aim to examine the relationship between LA strain and future atrial fibrillation (AF) events in ESUS patients.