Left atrial appendage: structure, function, imaging modalities and therapeutic options.

The left atrial appendage (LAA) is a common source of cardiac thrombus formation and systemic embolism. It is a 'blind' cul-de-sac and multilobed anatomic structure with variable anatomy. Therefore, it requires detailed evaluation in multiple imaging planes to evaluate for thrombus formation. Transesophageal echocardiography is the most common imaging modality used to rule out LAA thrombus. Doppler imaging enhances understanding of LAA function. 3D imaging of the LAA with live 3D transesophageal echocardiography, computed tomography and MRI may be further utilized for thrombus detection, as well as for sizing, and the development of new transcatheter occluder devices for LAA to prevent thrombus formation is needed.