The human heart has four chambers. The two upper chambers are called the atria. The two lower chambers are called the ventricles. While the ventricles do most of the work of moving blood from the heart to the rest of the body, the atria help by drawing blood into the heart. Enlargement of any of the heart's structures (cardiomegaly) usually signals increased pressure at one point in the circulation.

Blood Pressure

Blood pressure in the body is carefully controlled by several mechanisms and the anatomy of the body's blood vessels. If the blood vessels become hardened, a condition known as atherosclerosis, blood pressure increases. To overcome this increase in blood pressure, the heart works harder. Because it is made of muscle, the heart starts to become enlarged at the ventricles, which are the main structures involved in pushing blood out to the body.

Heart Valves

Dividing the different chambers of the heart are two valves, one on each side. On the right side is the tricuspid valve. On the left side is the mitral valve. Stenosis, or narrowing of the valves, causes increased blood pressure between the atria and the ventricles. To counter this pressure, the atrial walls increase in size and strength, pushing the blood more forcefully into the ventricles.

Mild Atrial Enlargement

As mentioned, if the heart valves between the atria and the ventricles are abnormal for any reason, the atria become enlarged. Some heart valve diseases are acquired, as is the case in high blood pressure from poor diet and exercise. Other conditions are inherited, as is the case in mitral valve defects. Still other conditions that lead to atrial enlargement are idiopathic, meaning that no clear cause is identified.

Diagnosis

While the symptoms of an enlarged heart or heart structure are not immediately recognizable, some symptoms like shortness of breath, chest congestion and chest pain may signal health care providers to perform tests for cardiomegaly. The simplest test is an electrocardiogram (EKG). The EKG detects abnormalities in the electrical circuitry of the heart. Different EKG patterns signal different abnormalities, so a trained provider will recognize atrial enlargement based on an EKG reading. Other studies, such as ultrasound visualization of the heart, are available if the EKG reading is inconclusive.

Treatment

Treatment of an enlarged heart or heart structure can be as simple as a change in diet and exercise regimens to medication and even surgery. Diet and exercise are a good, natural way to reduce blood pressure and promote better heart health. Certain medications can be prescribed by health care providers to help reduce blood pressure and reduce the stress on the heart. If the heart valve defects do not respond to medication, surgery to repair or replace the valves may be necessary.