Left Atrial Strain and Cryptogenic Stroke

Overview

Cryptogenic stroke is a type of stroke in which the cause of the blood clot cannot be identified, leaving many patients without a clear treatment plan and at high risk for another stroke. Current medical guidelines recommend blood-thinning medication (anticoagulation) only when atrial fibrillation (AF) -an irregular heart rhythm- can be documented. However, AF may occur silently and remain undetected. Long term implantable (placed invasively under the skin) devices may be needed to capture these episodes. AF is known to develop from disease of the left atrium, the upper chamber of the heart that receives blood from the lungs. When the left atrium does not contract normally, blood flow may slow down, increasing the risk of clot formation. Nowadays, the left atrial (LA) function can be quantified precisely using a noninvasive ultrasound technique called strain imaging. This study aims to determine whether reduced LA function is associated with cryptogenic stroke and its recurrence even when AF is not observed. If such an association is confirmed, LA strain could serve as a new biomarker to identify patients at risk, earlier than the development of overt AF, enhance preventive measures to reduce recurrent strokes. Because echocardiographic strain imaging is safe, cost-effective, and widely available, it may become an important tool for improving care in this high-risk population.

Cryptogenic stroke accounts for nearly one-third of ischemic strokes, yet its underlying mechanism often remains unidentified, leaving patients without targeted therapy. Atrial fibrillation (AF) is detected up to one third of cryptogenic strokes, but its detection frequently requires prolonged monitoring due to subclinical paroxysmal episodes. Increasing evidence suggests that structural and functional abnormalities of the left atrium (LA) precede AF and contribute to thromboembolic risk independently of rhythm disturbances. This multicenter retrospective study aims to determine whether impaired LA strain, a sensitive echocardiographic measure of atrial function, is associated with cryptogenic stroke and can predict recurrent events. Echocardiographic images of the patients who were referred to the echocardiography laboratory as part of stroke work up will be analyzed offline, using standardized speckle-tracking software. De-identified clinical and imaging data will be collected in the central core laboratory at the University of Pittsburgh for uniform analysis and validation. By establishing LA strain as a biomarker of atrial cardiopathy and cryptogenic stroke risk, this study seeks to bridge the current gap between stroke classification and management. Demonstrating the independent association between LA dysfunction and cryptogenic stroke and the recurrence of cryptogenic stroke independently of AF could support the use of LA strain as a risk marker to for monitoring patient and developing preventive strategies such as anticoagulation without documented AF. Hence, our findings may improve preventive care and reduce the burden of disabilities due to cryptogenic stroke.