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The Left Atrium |
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Written by : Shahdad Azmoon, MD Date of Publication : October 23, 2005
The Left Atrium of the Heart
The left atrium is the chamber of the heart that lies more posteriorly and receives oxygenated blood from the lungs. Blood from the left atrium is then pumped into the left ventricle where pressure maybe generated to pump the oxygenated blood throughout the human body. The left atrium simulates a temporary storage space while the left ventricle is pumping out oxygenated blood it had previously received from the left atrium. The valve lies in between the left atrium and the left ventricle and whose job is to control the flow of blood between the two chambers is called the mitral valve. While the left atrium is receiving blood from the lungs, the mitral valve is closed. During this time the left ventricle is also pumping out oxygenated blood out of the heart for the rest of our body. When most of the blood in the left ventricle is pumped forward and out of the heart, the high pressures generated within the left ventricle slowly dissipate and the mitral valve opens to allow the oxygenated blood previously received from the lungs and temporarily stored in the left atrium to now pour into the left ventricle. Soon increasing pressures within the left ventricle begin to generate which facilitates the closure of the mitral valve which also produces the first heart sound.
The left atrium often dilates with age secondary to multiple cardiac co-morbidities some of which include mitral valve disease, hypertrophic cardiomyopathy, left ventricular diseases, diastolic dysfunction, rheumatic disease, chronic atrial fibrillation (1).
The left atrium is susceptible to thrombosis formation in atrial fibrillation. When imaging the left atrium trans-esophageal echocardiography (TEE) is both more sensitive and specific in detecting thrombi (2). Hwang and colleagues reported a 93 percent sensitivity with 100 percent specificity for thrombus detection using TEE (3). The TEE will also provide better imaging and examination of most of the atrium including the most posterior wall which most often may not be visible via trans-thoracic echocardiography (TTE).
Dilation of the left atrium itself may promote atrial fibrillation due to inability of propagation of orderly depolarization.
The left atrium may be involved as part of amyloid cardiomyopathy.
Neoplasm formation of the left atrium are rare and most often are benign. However enlargement of such tumors may obstruct flow of blood as well as form a nidus for thrombo-embolic disease. The left atrium may also be compressed from the outside by intra-thoracic neoplasms, as well as fluid around the heart, spinal deformities, aortic aneurysms and hiatal hernias.
Bibliography
1. Sanfilippo, AJ, Abascal, VM, Sheehan, M, et al. Atrial enlargement as a consequence of atrial fibrillation. A prospective echocardiographic study [see comments]. Circulation 1990; 82:792.
2. Manning WJ, Weintraub, RM, Waksmonski, CA, et al. Accuracy of transesophageal echocardiography for identifying left atrial thrombi. A prospective, intraoperative study. Ann Intern Med 1995; 123:817.
3. Hwang, JJ, Chen, JJ, Lin, SC, et al. Diagnostic accuracy of transesophageal echocardiography for detecting left atrial thrombi in patients with rheumatic heart disease having undergone mitral valve operations. Am J Cardiol 1993; 72:677.
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