Mitral regurgitation (MR) is a condition whereby an injury or disease has resulted in the mitral valve becoming leaky through not closing properly, causing blood to regurgitate backwards into the left atrium (LA) from the left ventricle (LV) during systole (contraction). This can result in blood backing up into the lungs.
Alternative Names:
Mitral Insufficiency or Mitral Incompetence.
Incidence:
1 in 5 over the age of fifty-five (Western world) have some form of mitral regurgitation.
The Normal Valve:
The mitral valve consists of two triangular shaped flaps called leaflets. These are attached to the heart muscle via a ring called the annulus. The mitral valve is attached to the left ventricle by chordae tendineae cordis, which resemble the strings of a parachute. When working properly, the mitral valve closes fully, preventing blood from passing back into the left atrium during systole of the left ventricle.
Causes:
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Mitral Valve Prolapse: A condition whereby the cordae and leaflets become weakened causing the prolapse of the valve back into the left atrium as the left ventricle contracts.
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Annular Dilatation.
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Ruptured papillary muscle or chordae tendineae due to acute myocardial infarction or trauma.
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Rheumatic Fever: a complication, which can sometimes occur following streptococcal infection. It is still common in parts of the third world and its reduced incidence in the western world has correlated with improved public health and routine use of penicillin.
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Endocarditis: Infection involving the heart valves whereby growths or vegetation can develop on the surface. This can result in perforation of the mitral leaflet.
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Congenital heart disease: some babies are born with leaky valves and there is a strong association between certain types of defects in the atrial septum and cleft mitral valves which can leak severely.
Symptoms: Acute vs Chronic
Acute - Breathless symptoms that occur suddenly may be result of an acute mitral regurgitation which can be secondary to either papillary muscle rupture or its function in acute myocardial infarction (MI), or rupture chordae tendineae. These patients often present directly to the A&E Department.
Symptoms include:
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Severe shortness of breath.
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Heart Palpitations - rapid or irregular.
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Chest pain (only in context of MI)
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Cough (can be productive of white sputum).
Chronic - Symptoms that have been occurring for a longer period (can be several years) is referred to as chronic mitral regurgitation.
Symptoms include:
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Shortness of breath - particularly when laying flat or exercising.
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Heart Palpitations - rapid or irregular.
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Cough.
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Increased fatigue – due to reduced cardiac output.
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Swollen ankles or feet due to increased fluid.
Diagnosis:
Stethoscope – Can often be identified by a characteristic “whooshing” sound in systole. Referred to as a heart murmur, due to the sound of turbulent blood passing from the left ventricle into the left atrium.
Echocardiogram and Transoesophageal Echo (TOE) – Cardiac ultrasound can determine the efficiency of the left ventricle during contraction, and using colour Doppler can visualise a leaky valve. Continuous Wave (CW) jet can be used to determine the intensity.
ECG - Atrial Fibrillation due to left atrium enlargement.
Cardiac Catheterisation – Performing a left ventriculogram can demonstrate the flow of contrast back into the atrium during systole. During a right heart cath there is also a significant increase in V wave size of the Pulmonary Capillary Wedge (PCW) pressure.
Chest X-ray – The left ventricle can often be enlarged. This can be seen on a chest x-ray by the left side of the heart being enlarged, which may indicate a leaky valve. Pulmonary Oedema is also a possible sign of the presence of MR.
Pathophysiology:
When MR is present the LV becomes enlarged due to the creation of two outlets (aorta and left atrium) as it tries to compensate for the decreased output.
Medical Treatment:
Medication won’t fix the damaged valve but they can reduce heart size and annular dilatation reducing MR.
Diuretics – Used to reduce the fluid build-up in the lower legs and lungs.
ACE Inhibitors – These dilate the arteries reducing the workload on the heart, which in turn reduces the amount of regurgitation into the left atrium.
Surgical Treatments:
Valve repair is performed if the valve is only partially damaged. Valve Replacement occurs if the valve can’t be repaired.
Valve Repair – This is achieved by repairing either the leaflets or valve tissue so it can close tightly. An example of this is an annuplasty ring which is sewn on the left atrial aspect of the valve.
Valve Replacement - In this procedure the surgeon removes the damaged mitral valve and replaces it with an artificial version. There are two types of valves available: Mechanical and Biological.
Mechanical: These valves are made of metal and as such are easily shown on x-ray. These valves last a long time however may result in clot formation around the device. For this reason the patient must medicated with an anticoagulant, such as warfarin to prevent the formation of clots which may detach and cause a stroke.
An example of this device is the St Jude Masters Series Mechanical Heart Valve as seen above.
Biological: These are tissue valves often removed from a pig. Referred to as bioprostheses, these valves don’t last as long as mechanical valves however allow the patient not to use long-term anticoagulants.
Percutaneous Treatments:
This treatment is relatively new, however companies such as Evalve Inc., produce the MitraClip™ to allow cardiologists to repair the mitral valve in the cath lab. Turn over the page for a full review on this technique which is still undergoing clinical trials.
References:
1. ‘Mitral valve regurgitation’, Mayo Clinic website: http://www.mayoclinic.com/health/mitral-valve-regurgitation/DS00421/DSECTION=1
