Causes and Treatment of Mitral Regurgitation

Mitral regurgitation occurs when the heart's mitral valve does not close properly, allowing blood to leak (regurgitate) back into the heart chamber. Mitral regurgitation is not only the most common of heart valve abnormality, but it can also be one of the most challenging to evaluate and treat.

Understanding Mitral Regurgitation

The mitral valve separates the left atrium of the heart from the left ventricle. When the left atrium contracts, the mitral valve opens to allow blood into the left ventricle. When the left ventricle contracts, the valve shuts to prevent a backflow of blood.

In mitral regurgitation, the leaky valve places added pressure on the heart which can lead to an enlargement of the heart muscle and long-term, irreversible damage.

There are a number of conditions that can mitral regurgitation:

• Mitral valve prolapse (bulging of the valve "doors")
• Endocarditis (including infection of the heart valves)
• Myocardial infarction (heart attack)
• Dilated cardiomyopathy (enlargement of the heart)
• Hypertrophic cardiomyopathy (thickening of the heart muscle)
• Rheumatic heart disease (mostly seen in developing countries)

Complications

Mitral regurgitation is usually a chronic condition that progresses slowly over the course of years. During this time, the pressure in the left atrium will increase due to the extra blood regurgitated back into the chamber. Over time, this pressure will cause the heart to enlarge. When this happens, a person will often experience:

• Dyspnea (shortness of breath)
• Atrial fibrillation (an irregular and often rapid heartbeat)
• Syncope (fainting)

Chronic mitral regurgitation also places added strain on the left ventricle, forcing it to work harder to pump blood into the body. This extra work can cause the muscle to thicken, leading to enlargement and, in some cases, heart failure. By the time this occurs, the muscle is usually irreversibly damaged, making replacement of the valve all the more dangerous.

On rare occasion, mitral regurgitation may develop suddenly, most often during a heart attack of a severe episode of endocarditis. If this happens, it will typically cause pulmonary edema (the buildup of fluid in the lungs) and a dangerous drop in blood pressure. Acute mitral regurgitation is always considered a medical emergency and, if not treated immediately, can result in death.

Treatment

Treatment of mitral regurgitation will largely depend on the stage of the illness and the condition of the heart itself. Since it is a problem affecting the mechanics of the valve, treatment will more often than not involve surgery or an invasive procedure.

Two surgical approaches are standardly used:

• Mitral valve replacement involves the use of either a man-made valve or a heart valve taken from an animal (usually a pig). While both can work equally well, clotting is common with mechanical valves and requires chronic medications to thin the blood. On the other hand, mechanical valves generally last longer so they may be more appropriate for younger patients under 65.
• Mitral valve repair requires the surgeon to literally reshape the valve to reduce or eliminate regurgitation. It is a skilled technique requiring a highly experienced specialist. Overall, death due to surgery is generally lower than valve replacement and offers longer survival times. Pre-operative evaluation will need to be done to decide whether a repair is a feasible option.

Other Treatment Options

There are times when a person may not be a candidate for surgery. In such a case, treatment will be focused on minimizing symptoms and/or relieving pressure on the heart. Among the current options:

• Vasodilators (a type of drug used to dilate blood vessels) are sometimes used but do little to improve long-term outcomes. ACE inhibitors such as Vasotec (enalapril) or Capoten (captopril) are the most common choices.
• Cardiac resynchronization therapy (CRT) involves the use of a special pacemaker which paces both the right and left ventricles simultaneously. CRT is most often used when there is left ventricular enlargement.
• Endocarditis prophylaxis involves the use of antibiotics to prevent infection in the heart’s inner lining. It is today used only in rare cases.