Introduction: Mitral stenosis (MS) causes structural and functional abnormalitiesof the left atrium (LA) and left atrial appendage (LAA), and studies show that LAA performance improves within a short time after percutaneous transvenous mitral commissurotomy (PTMC). This study aimed to investigate the effects of PTMC on leftatrial function by transesophageal echocardiography (TEE).Methods: We enrolled 56 patients with severe mitral stenosis (valve area less than1.5 CM2). All participants underwent mitral valvuloplasty; they also underwenttransesophageal echocardiography before and at least one month after PTMC.Results: Underlying heart rhythm was sinus rhythm (SR) in 28 patients and atrialfibrillation (AF) in remainder 28 cases. There was no significant change in the leftventricular ejection fraction (LVEF), left ventricular end diastolic dimension (LVEDD),or the left ventricular end systolic dimension (LVESD) before and after PTMC in bothgroups. However, both groups showed a significant decrease in the left atrial volumeindex (LAVI) following PTMC (P=0.032 in SR and P=0.015 in AF group). LAA ejectionfraction (LAAEF) and the LAA emptying velocity (LAAEV) were improved significantlyafter PTMC in both groups with SR and AF (P<0.001 for both).Conclusion: Percutaneous transvenous mitral commissurotomy improves left atrial appendage function in patients with mitral stenosis irrespective of the underlying heart rhythm.