The left atrial appendage is a small structure that resembles a finger coming off the left atrium of the human heart. The appendage fills with blood and releases blood into the left ventricle at the same time as the left atrium. Though this structure is not necessary to survival, it plays a role in lowering the blood pressure against the left side of the left atrium. Problems with the left atrium can lead to the removal of the left atrial appendage in some cases.
The left atrial appendage is hollow and fills with blood when the left atrium does. The muscles in this appendage run parallel to the muscles in the left atrium. It is located on top of the left atrioventricular groove. In heart surgery, this appendage must sometimes be moved out of the way because its location partially obstructs access to the left coronary artery.
The size of this appendage changes with relation to a person’s age and sex. It is in the shape of a curved, elliptical tube and can have two or more lobes that come off to the sides of it. The opening to this chamber is, on average, between 0.2 and 0.5 inches (about 0.6 and 1.2 cm). It is generally between 0.8 and 1.1 inches (about 2.1 and 2.9 cm) long, though in some individuals, it can measure up to 1.7 inches (about 4.5 cm) in length.
Atrial fibrillation, which is an irregularity in a person’s heartbeat caused by a misfiring electrical impulse in one or both atria, can cause problems in the appendage. This condition is responsible for about 25% of strokes, which are caused when blood flow to the brain is disrupted, usually through a blood clot becoming lodged in an artery leading to the brain. In patients with atrial fibrillation, blood may collect in the left atrial appendage; if it breaks loose, it can lead to stroke. Some doctors recommend removing the appendage to prevent deaths related to stroke.
Humans can easily survive without the use of the left atrial appendage. Patients who have needed mitral valve surgery have often had this appendage removed as a routine part of that surgery. There is currently no evidence that removing this section of the heart adversely affects heart function over the life of a patient. Though this appendage is expendable, there is evidence to suggest that it can assist in lowering the blood pressure in the left atrium.