Mitral regurgitation, also known as mitral insufficiency, refers to the retrograde flow of blood through the mitral valve from the left ventricle to the left atrium during systole due to anomalies of the mitral valve or the papillary muscles.
Myocardial infarction involving supply to the papillary muscles can cause them not to function properly, leading to mitral insufficiency.
mitral valve prolapse is the most common cause of mitral regurgitation as the prolapsed and “floppy” valve is unable to hold against the pressure differences experienced during ventricular systole.
Intrinsic valvular damage can be caused by infective endocarditis and rheumatic fever.
Diseases that cause dilation of the left ventricle (e.g. aortic stenosis, aortic regurgitation) can lead to mitral regurgitation by stretching the mitral valve annulus.
Rarely, ergotamine, pergolide, and cabergoline can cause mitral regurgitation. Note that this is far less common than other etiologies, and should only be considered as a possibility after having ruled out others definitively--even if a patient is taking one of these drugs!
Acute mitral regurgitation can cause acute heart failure
Acute mitral regurgitation presents with jugular venous distention and sudden onset of congestive heart failure, while chronic disease presents with an apical thrill without signs of congestive heart failure.
Acute mitral regurgitation presents with the rapid onset of severe congestive heart failure with a low cardiac output, and is commonly due to rupture of a recently infarcted papillary muscle (i.e. a patient who has suffered a myocardial infarction within the past couple of days).
In acute onset mitral regurgitation, the left atrium is unable to remodel rapidly enough to accommodate the increased volume. This leads to a rapid increase in left atrial filling pressure, resulting in increased pulmonary capillary pressure and pulmonary edema.
Patients with chronic mitral regurgitation may be asymptomatic with normal exercise tolerance; however, they are often sensitive to shifts in volume status and may be at risk for development of acute volume overload (flash pulmonary edema) and right-sided heart failure.
Mitral regurgitation causes a high-pitched holosystolic murmur at the apex with radiation to the axilla. Remember that mitral regurgitation often occurs in patients with mitral valve prolapse, so the murmur of mitral regurgitation may co-occur with a mid-systolic click.
Electrocardiogram (ECG) findings in chronic disease may include notched P waves referred to as P mitrale, which may also be observed in the setting of mitral stenosis and other left atrial overload states. Over time, mitral regurgitation may lead to atrial fibrillation.
Dilation of the left atrium in chronic mitral regurgitation leads to an enlarged cardiac silhouette on chest X-ray.
The diagnostic modality of choice is echocardiography with color Doppler, which demonstrates regurgitant flow.
Mitral regurgitation may cause a widely split S2 as the regurgitant flow leads to earlier emptying of the left ventricle, allowing the aortic valve to close much earlier than the pulmonic valve.
Mitral regurgitation can be associated with an S3 heart sound.
Medical management is indicated in symptomatic patients with the goal of reducing afterload and thus regurgitant flow. Agents used include:
Open mitral valve replacement is curative, and is indicated in the setting of very severe, symptomatic disease. Synthetic valves require ongoing anticoagulation and biosynthetic valves have a limited lifespan, making valve repair the treatment of choice in patients with a valve intact enough to withstand the procedure.