Informed consent will be obtained prior to any research related procedures Prior to performing the transesophageal echocardiography, 4 and a 2-chamber transthoracic images will be obtained to perform standard left atrial volumetric assessment as well as speckle tracking interrogation. Both these procedures will be performed offline. The transesophageal echocardiography will be performed using available equipment with a 5- to 7-megaHertz multiplane transducer and according to standard of care. All images will be acquired per American Society of Echocardiography guidelines and will be recorded for further analysis. The left atrial appendage will be best visualized in the 60, 90 and 110 degree imaging planes and left atrial appendage contraction velocity will be recorded by placing a pulsed wave Doppler sample volume inside the proximal third of the left atrial appendage at each angle. In addition, images will be recorded using a 3-beat cycle capture to later perform offline velocity vector imaging analysis for left atrial appendage speckle tracking analysis. The transthoracic echocardiography will be performed just before the transesophageal echocardiography examination using a 2- to 4-megaHertz transducer and according to standard practice guidelines. The following echocardiographic variables will be prospectively measured and calculated: left ventricle ejection fraction using Simpson method, left atrial volume will be measured using biplane method and left atrium volume index is calculated based on body surface area. Tissue Doppler images of mitral valve annulus will be measured and Pulsed wave Doppler of mitral inflow velocity.