What Is Mitral Regurgitation?Mitral regurgitation (MR) occurs when the heart's mitral valve does not close completely, allowing blood to regurgitate (or "leak") through the valve when it should be closed.
The mitral valve is the cardiac valve that separates the left atrium from the left ventricle. When the left atrium contracts, the mitral valve opens to allow blood to flow into the left ventricle. When the left ventricle subsequently contracts (to eject blood into the aorta to supply the body's needs), the mitral valve closes, in order to prevent a backflow of blood into the left atrium.
In MR, because the valve is "leaky," blood regurgitates back into the left atrium when the left ventricle contracts.
What Are The Causes of Mitral Regurgitation?There are several cardiac conditions that can produce MR. These include:
- Mitral valve prolapse
- Endocarditis (infection of the heart valves)
- Trauma (which can damage the structure of the mitral valve)
- Rheumatic heart disease (which is now uncommon in developed countries)
- Heart attack or myocardial infarction (which can cause damage to the papillary muscles, the heart muscles that support the mitral valve)
- Dilated cardiomyopathy (enlargement of the left ventricle can disrupt the normal mechanism of the mitral valve)
- Hypertrophic cardiomyopathy (the thickening of the left ventricular muscle can disrupt the normal mechanism of the mitral valve)
What Problems Does Mitral Regurgitation Produce?In the vast majority of cases, mitral regurgitation progresses relatively slowly, over months or years -- a condition called chronic MR. During this gradual process, the pressure within the left atrium increases (due to the "extra" blood that regurgitates into the left atrium), and eventually the left atrium becomes enlarged. These changes in the left atrium can lead to shortness of breath, and can also produce atrial fibrillation.
Chronic MR also places extra strain on the left ventricle, which has to work harder in order to supply the body with the proper amount of blood flow. This extra work can cause the muscle of the left ventricle to thicken, and/or the ventricle may become enlarged. Eventually, this can lead to heart failure.
Unfortunately, by the time significant heart failure develops from MR, the muscle of the left ventricle has likely become irreversibly damaged. At that point, repairing or replacing the mitral valve is much more dangerous, and may not significantly improve the heart's function. Therefore, if you have chronic MR, it is important for your doctor to follow your condition closely to prevent the left ventricle from developing irreversible muscle damage.
On rare occasions, severe MR may occur suddenly, most often during an acute myocardial infarction (heart attack) or during endocarditis (infection of the heart valves). Acute MR is always a medical emergency. This condition can cause the lungs to fill rapidly with fluid, producing a condition called "pulmonary edema", which leads to severe shortness of breath. Acute MR can also dramatically reduce the amount of blood the heart can pump to the body's tissues, producing extremely low blood pressure, weakness, and dizziness. This acute form of MR is often fatal, and effective treatment requires immediate and aggressive medical stabilization in an intensive care unit, as well as surgical repair.
Treating Mitral RegurgitationIf you have MR, your treatment will depend on the "stage" of the condition (that is, how the MR is affecting your symptoms and the overall condition of your heart).
Bonow, RO, Carabello, BA, Chatterjee, K, et al. 2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation 2008; 118:e523.
Vahanian, A, Baumgartner, H, Bax, J, et al. Guidelines on the management of valvular heart disease: The Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology. Eur Heart J 2007; 28:230.