Echocardiographic Predictors of Atrial Fibrillation

This study is using echocardiography (heart ultrasound) to look for signs in the heart that might predict which stroke patients — specifically those with a stroke of unknown cause — are at risk of developing atrial fibrillation (an irregular heart rhythm that can cause further strokes). **You may be eligible if...** - You are 18 or older - You have had an ischemic stroke or a brief stroke-like episode (TIA) confirmed by brain imaging - Your stroke was classified as "embolic stroke of undetermined source" (ESUS) or "cryptogenic" - OR you have been newly diagnosed with atrial fibrillation **You may NOT be eligible if...** - Your stroke was caused by a large artery blockage or a known heart clot source - You have a known major heart condition already explaining the stroke - You are unable to give informed consent Talk to your doctor to see if this trial is right for you.