An incidentally discovered left atrial appendage membrane: case report and literature review.

The left atrial appendage (LAA) is an extension of the left wall of the atrium and its close anatomic relationship to the free wall of the left ventricle gives it anatomic characteristics distinct from the left atrium. To date, only seven cases involving a LAA membrane have been described. A patient with an incidentally discovered, partially obstructive membrane at the orifice of the LAA, causing functional stenosis is presented, and our case is compared to those in the existing literature. The clinical significance of LAA membranes remains unknown. These rare membranes are usually an incidental finding on transesophageal echocardiogram during evaluation of an atrial dysrhythmia. It is not clear if these membranes could be promoting atrial fibrillation or if the association is merely a result of sampling bias. These membranes may also affect cardioembolic risk. Finally, the increasing use of percutaneous catheter-based therapies such as radiofrequency ablation and occlusion of the left atrial appendage, will likely result in the increasingly frequent identification of these membranes, and when present may increase the technical difficulty associated with these catheter-based therapies.