An enlarged left atrium means that the left upper chamber of the heart is working harder than it should, causing it to get larger than normal. The enlargement may be due to high blood pressure, a faulty heart valve, ageing or obesity. In the process, the atrium thickens to pump harder. Without treatment, it can cause serious complications.
Any factor that contributes to high blood pressure taxes the heart and can enlarge the left atrium. These include ageing, high blood pressure, obesity and diseases such as cardiomyopathy, or a thickening of the aorta, which is the large artery leaving the heart.
A common cause of left atrial enlargement is a faulty mitral valve. If the valve doesn't close properly, the left atrium can't pump blood completely into left ventricle. Blood make back up into the left atrium, causing pressure that enlarges it. The mitral valve can be damaged due to rheumatic fever, a birth defect, calcium deposits, tumours, radiation therapy to the chest or some medicines.
Hypertrophic cardiomyopathy is a group of diseases in which the lower chambers of the heart develop thickened walls. Because the muscle walls become stiff, the mitral valve may not be able to close properly.
An individual with left atrial enlargement may get tired easily, especially when involved in physical activity, and experience shortness of breath, heart palpitations or have swollen ankles or feet. Other signs may include bouts of bronchitis or heavy coughing, sometimes with blood in the sputum.
Without treatment, an enlarged left atrium can lead to heart failure, a build-up of blood pressure and fluid in the lungs, and atrial fibrillation, a condition in which the upper chambers of the heart beat wildly and rapidly. This makes the atria less able to pump blood out of the heart. Blood can pool and clot in the atria. There is a risk that clots can break apart, flow through the blood vessels and block arteries leading to the brain, causing a stroke.
Chest X-rays and electrocardiography are used to pinpoint whether atrial enlargement is due to mitral valve disorders, a narrowing of the mitral valve or a build-up of pressure inside the heart.
The specific treatment used depends on the cause of the enlargement. Mitral valves can be repaired or replaced, and drugs such as beta blockers and the calcium channel blocker verapamil cause the heart muscle to contract more gently. This allows the atria to fill more completely and flow between the heart's chambers more easily. A cardioverter-defribrillator can be implanted in the body to help control atrial fibrillation. In severe cases, surgery or alcohol ablation can be performed to thin the walls of the heart and improve blood flow.