Left Auricle of the Heart

Description

Positioned on the superior and leftward aspect of the cardiac silhouette, the left auricle (auricula atrii sinistri) projects anterolaterally from the left atrium as an ear-like muscular pouch. Its trabeculated wall contrasts with the smoother body of the left atrium lying posteriorly, and it drapes over the root of the pulmonary trunk and adjacent left coronary sulcus. Epicardial coronary vessels course across the anterior surface of the myocardium, with the left coronary artery and its circumflex branch running in the atrioventricular groove near the base of the auricle. Major great vessels frame the heart in situ, including the ascending aorta centrally and the superior vena cava to the right. Clinically, the left atrial appendage is the dominant site of thrombus formation in nonvalvular atrial fibrillation, a detail that makes its external contour and relationship to the pulmonary trunk and left coronary circulation worth teaching precisely. Electrophysiology and structural heart teams target this anatomy during left atrial appendage occlusion (for example, Watchman-type devices) and during surgical ligation, where neighboring structures such as the circumflex artery can be at risk. Transesophageal echocardiography and cardiac CT both hinge on a clear mental model of this appendage’s position and its narrow ostium relative to the left atrium. Cardiothoracic anatomy courses, cardiology board review materials, and patient-facing explanations of atrial fibrillation stroke risk will all benefit from this in-chest depiction that keeps the auricle anchored to the surrounding great vessels and rib cage. It also suits atlases and operative primers discussing left atrial appendage closure, pericardial access, and coronary surface landmarks. Anatomical accuracy verified by SciePro's Medical Advisory Board.