Anatomical description of malformations of the neck of the left atrial appendage.

The recently-described left atrial appendage (LAA) neck is a truncated cone-shaped structure that connects the LAA orifice to its lobe. It shows malformations in some cases, but their exact description and clinical significance are unknown. Therefore, the aim of this study was to provide a detailed anatomical and morphometric analysis of LAA neck malformations in clinical context. A total of 250 autopsied human hearts (20.0% women, 46.7 ± 18.2 years old) were examined for mural malformations: spikes and bulges. Endocardial roughness of the LAA neck with a depth <2 mm and no recognizable epicardial protrusion was defined as ectopic trabeculation. LAA neck malformations were found in 13.6%, bulges in 10.0% of the hearts examined, spikes in only 3.2%, and ectopic trabeculations in 24.8%. In one case, both a bulge and a spike were found in the LAA neck. Most LAA neck roughness was observed on the aortic and venous surfaces of the LAA neck. Those surfaces were the most common locations for malformations and ectopic trabeculations. The LAA wall was significantly thinner than the surrounding neck wall within the bulges and the ectopic trabeculations, but not in the spikes.