In a normal heart, the flow of blood between the atria and ventricles (upper and lower chambers), and blood flow out of the heart, is regulated by four valves. These valves are made from thin flaps of tissue. They only open one way, and only at the right time, to keep blood flowing in the right direction.

In some cases, however, a valve may be diseased or otherwise unable to function normally. This may result in blood flowing backward (e.g. from the left ventricle to the left atrium). This condition is known as valvular regurgitation, or alternatively, as valvular incompetence or valvular insufficiency. Valvular regurgitation may occur in any of the four valves of the heart: the aortic valve, the mitral valve, the tricuspid valve or the pulmonic valve. Depending on the severity of the leak, there can be as much as two drops of blood that leak backward for every three drops of blood that travel forward.

Valvular regurgitation may prevent the heart from circulating enough blood to the lungs or tissues and organs of the body. To compensate, the left and right ventricles (pumping chambers of the heart) must work harder. As a result, one or both ventricles may eventually be damaged from the increased workload. This damage may be accompanied by myocardial (heart muscle) dilation and hypertrophy (thickening and enlargement of the heart). In the most severe cases, valvular regurgitation could lead to heart failure, a condition in which the heart cannot pump enough blood to satisfy the body, and the  lungs become congested with fluid and/or the legs become swollen (edema).

Valvular heart disease may be either congenital (developed before birth) or acquired as a result of conditions such as:

Researchers are continually exploring other possible causes of valvular regurgitation. Radiation cancer therapy, for example, often increases the risk of medical complications secondary to the disease itself, particularly when used in combination with some chemotherapy drugs. Depending on the location of the tumor, radiation may be directed to the underarms, neck and chest. This is known as mantle field radiation. Inverted Y radiation is used for the abdomen, spleen, pelvis or groin. With mantle field radiation – especially at high doses – there is potentially latent damage to the throat, lungs, thyroid and heart. Areas of the heart that may be affected include:

• Pericardium (outer tissue layer)
• Myocardium (heart muscle itself)
• valves and arteries
• Blood vessels leading to the heart

It is important, therefore, to have regular follow-up examinations with physicians knowledgeable about the effects of chemotherapy and radiotherapy on a particular area of the body. Ongoing research has included testing of newer types of radiation therapy, with the ability to “mold” its beam according to the shape and size of the tumor. This would greatly minimize its impact on surrounding tissues and organs and, therefore, the risk of long-term problems.