Incidence and clinical relevance of left atrial appendage membranes: a new congenital heart disease?

Aims: Left atrial appendage (LAA) membranes are rare congenital anomalies. Those involving the appendage orifice may obstruct its emptying flows, thus promoting blood stasis and clot formation. However, the epidemiology of LAA membranes has never been studied and a correlation with appendage thrombosis has never been proved. Very few case reports described LAA membranes, therefore, their frequency and clinical significance are not known. Moreover, their presence and degree are of crucial importance in planning LAA percutaneous closure, a procedure whose indication is evolving, and whether their presence can represent technical issues during the device implantation is not known. This study aimed to evaluate the incidence and the clinical significance of LAA membranes.

Methods and results: A population of 6030 consecutive transoesophageal echo (TOE) studies has been retrospectively reviewed in order to find those patients in whom an LAA membrane has been found. A literature research has been performed to review previous described cases. Among 6030 TOE cases, an LAA membrane has been described in 6 (prevalence of 1/1000). In one case, the membrane was associated to a severe LAA hypoplasia and in another case to an LAA thrombus (these represent the first cases ever described). All patients had an atrial fibrillation (AF) history and two were in AF during the TOE exam.

Conclusion: LAA membranes are rare congenital abnormalities occasionally discovered during a TOE exam, frequently in patients affected by AF. In half of the cases, they obstruct the LAA flow, thus theoretically pre-disposing to clot formation. They may be rarely associated to an appendage hypoplasia. During a TOE exam, cardiac imagers should always rule out their presence.