Purpose: Left atrial (LA) and left ventricular (LV) remodelling may lead to stroke. The aim of this study was toanalyze LA function and LV strain in patients with embolic stroke of undetermined source (ESUS).Material and methods: This prospective study included 35 ESUS patients and 37 age and sex-matchedcontrols. All participants underwent brain computed tomography (CT), conventional and diffusion-weightedmagnetic resonance imaging (MRI), CT or MR angiography, 12 lead ECG, transthoracic echocardiography, and48 hour Holter ECG monitoring. LA volume and function were determined by echocardiography. LA reservoir andLV strains were measured longitudinally by speckle-tracking method. CHA2DS2-VASc, The National Institutesof Health Stroke Scale (NIHSS), modified Rankin Scale (mRS) scores were calculated.Results: Major cardiovascular risk factors were similar between the two groups. The mean CHA2DS2-VAScscore was 2.6±1.2. NIHSS was 3.9±3.0 and mRS was 1.3±0.8. Atrial electromechanical coupling intervals anddelays, LA emptying fraction and volumes were similar between the two groups. LA reservoir strain was lower thancontrols (25.2±7.2% vs. 29.7±8.8%, p=0,019). LV global longitudinal strain was lower than controls (-14.7±4.2%vs -16.4±3.9%, p=0,031). There was no correlation between LA, LV strains and the scores (CHA2DS2-VASc,NIHSS, mRS).Conclusions: ESUS patients had lower LA reservoir and LV longitudinal global strains than controls. Left atrialvolume index, LA emptying fraction did not differ between the two groups. Echocardiographic quantification ofLA and LV remodelling has great potential for secondary prevention from ESUS. Further studies are needed toconfirm our findings.