Obliteration of the left atrial appendage for prevention of thromboembolism.

Shaped like a wizard’s hat but long considered functionally insignificant, the conical, trabeculated left atrial appendage (LAA) arises from the embryonic left atrium during the third week of gestation and extends superiorly from the anterolateral surface of the left atrium (1). This accessory chamber extends over an area of 3 to 6 cm, is more compliant than the atrium, and is actively contractile in normal hearts—filling and emptying in response to both ventricular and atrial dynamics (2,3). Receptors in the LAA influence heart rate, and granules secrete atrial natriuretic peptide, contributing to regulation of intravascular pressure and volume in response to stretch (3–7).