The left atrium is the chamber of the heart that receives oxygenated blood from the lungs. The heart pumps blood from the left atrium, through the mitral valve, into the left ventricle and out to the body. Any condition that increases pressure in this portion of the system can lead to enlargement of the left atrium. These conditions may include hypertension, valve problems, heart failure or atrial fibrillation.
Hypertension
Pressure in the blood vessels of the body creates a force that the heart must overcome in order to pump blood. As this pressure elevates, the heart must work harder to perform its function. The heart, like any other muscle, enlarges when it is challenged. Elevated systemic blood pressure, called hypertension, makes the left side of the heart squeeze stronger to pump blood, and this exertion may lead to left atrial, as well as ventricular, enlargement.
Valvular Disorders
Blood moving from the left atrium into the left ventricle passes through the mitral valve. Impaired function and leaking of this valve is termed mitral regurgitation. Blood regurgitating, or bubbling up, from the left ventricle into the left atrium increases the pressure in the latter and can lead to enlargement, as noted by the Mayo Clinic.
Blood being pumped out of the left ventricle to the body goes through the aortic valve. This area may become narrowed or "stenotic," which forces the left side of the heart to squeeze harder to overcome the resulting resistance. As in high blood pressure, the increased resistance and work caused by valvular disorders can lead to left atrial enlargement.
Congestive Heart Failure
The American Heart Association describes congestive heart failure as the inability of the heart to squeeze and pump blood effectively. This condition, in turn, leads to a backup of fluid and, eventually, enlargement of the heart. The growth of the left ventricle is more prominent, but left atrial enlargement occurs as well.
Atrial Fibrillation
A physician diagnoses atrial fibrillation when the atria of the heart quiver instead of pumping rhythmically, according to the American Heart Association. The quivering impairs blood flow and increases pressure in the atria. Left atrial enlargement and atrial fibrillation frequently coexist.
Hypertrophic Cardiomyopathy
Hypertrophic cardiomyopathy is a condition in which the heart muscle becomes thickened. As the National Library of Medicine notes, this condition is often an inherited genetic disorder. The thickened muscle impairs the normal ability of the heart to contract, which alters blood flow. The disorder occurs in people of any age but is of particular concern among young athletes, as it can be associated with sudden death.
References
- National Library of Medicine: Hypertrophic Cardiomyopathy
- American Heart Association: Congestive Heart Failure
- The Mayo Clinic: Mitral Valve Regurgitation
- "British Medical Journal"; ABC of Clinical Electrocardiography: Conditions Affecting the Left Side of the Heart; J. Edhouse, R. K. Thakur and Jihad M. Khalil; May 2002
- American Heart Association: Atrial Fibrillation
