Mitral valve regurgitation (or mitral regurgitation) is a backflow of blood through the mitral valve of the heart during each contraction of the left atrium.
A defective mitral valve allows blood to flow in two directions during contraction:
- a part is pumped into the left ventricle;
- a variable amount of blood flows back to the left atrium via the mitral valve.
This valve defect can occur together with tricuspid regurgitation (blood reflux to the right atrium)
Causes of mitral regurgitation
An insignificant amount of mitral regurgitation (MR) exists in about 70 percent of adults.
Significant reflux (from moderate to severe) is much less common, in about 2 out of 100 people.
- A prolapse of the mitral valve that occurs when the tissue of the mitral valve is less elastic, deformed or bulging and therefore the valve leaflets do not completely close the heart valve.
The abnormal movement of the valve can cause blood to flow back from the left ventricle to the left atrium.
Although most people with mitral valve prolapse have only mild regurgitation, others develop significant disorders.
- Infective endocarditis is an inflammation of the heart and heart valves caused by bacteria, fungi or other organisms that invade the bloodstream. If the microorganisms succeed in colonizing and growing on the heart valves, platelets and fibrin are deposited on the heart valves. These neoplasms are called vegetation.
The vegetation can prevent a normal closure of the mitral valve, resulting in blood reflux.
A defective heart valve is much more susceptible to endocarditis than a normal heart valve.
- Rheumatic fever or rheumatic endocarditis is a condition that occurs when bacteria that cause a sore throat (such as streptococci) are not eliminated.
Rheumatic fever causes inflammation of the heart valves and other complications, such as the formation of nodules that hit the mitral valve and aortic valve.
- Connective tissue abnormalities: Barlow’s disease, Marfan syndrome and Ehlers-Danlos syndrome.
- Congenital anomalies (often hereditary) of the heart. Children born with certain types of heart abnormalities may develop mitral regurgitation.
- Other heart diseases – mitral regurgitation can occur after ischemia, myocardial infarction or heart muscle lesion.
- Thoracic trauma in rare cases causes tearing of the tendon threads that hold the mitral valve leaflets in place.
The injury of the tendon threads prevents a correct closure of the heart valve.
Types of mitral regurgitation
- Organic mitral regurgitation: occurs when components of the mitral valve are altered, for example, when the tendon threads of the valve have structural defects.
The most common form of organic mitral regurgitation is degenerative mitral valve regurgitation (floppy mitral valve), which may be characterized by myxomatous degeneration, i.e.:
- dilation of the outer ring,
- stretching or lesion of the tendon threads,
- Lengthening, thickening and loosening of the valve leaflets.
- Functional mitral regurgitation: when mitral regurgitation is present but not caused by structural changes in the heart valve.
The most common form is post-ischemic mitral valve degeneration, which occurs in patients who have already had a diagnosis of ischemic heart disease.
It is characterized by the dilation of the left ventricle, which causes a stretching of the valve ring (outer edge of the mitral valve).
The changes in the mitral valve are caused by the change in shape of the ventricle and its structures (especially papillary muscles and heart valve ring). The result is a restriction of movement of the heart valve leaflets.
Functional classification of mitral regurgitation according to Carpentier
- Grade I: Normal movement of the valve sails
- Grade II: Excessive movement of valve leaflets (mitral valve prolapse)
- Grade III: Restriction of movement
- Grade III a: valve opening with narrowing (stenosis)
- Grade III b: Flap closure with narrowing
Symptoms of mitral regurgitation
Symptoms depend on the severity and these include:
- Abnormal blood flow in the heart (heart murmur)
- Shortness of breath, especially under stress or lying down
- Fatigue, especially with increased activity
- Cough, especially at night or during sleep
- Palpitations — feeling of an accelerated heartbeat
- Swollen feet or ankles
Usually, the blood return at the mitral valve is mild and increases only slowly. You can’t feel any symptoms for decades.
Bradycardia can occur as a result of dilation of the left ventricle, which is related to mitral regurgitation.
Acute mitral regurgitation is an emergency: the return flow of blood occurs suddenly and massively, the heart is unable to compensate.
Characteristic symptoms are:
- acute pulmonary edema,
- severe shortness of breath, including at rest,
- severe heart failure.
In pregnancy, the effort that the heart has to make is increased. For this reason, women with mitral valve prolapse show the first symptoms of mitral regurgitation while pregnant.
Risks and complications
If mitral regurgitation is mild, it does not cause any problems, but if it increases, it can lead to the following complications:
Heart failure. In heart failure, the heart is unable to pump the amount of blood needed by the body.
The consequence of regurgitation at the mitral valve is pulmonary edema, which can lead to strong tension on the right side of the heart and cause ankle swelling.
Atrial fibrillation is an irregular heart rhythm in which the atria beat too quickly and in a disorderly manner.
Atrial fibrillation can cause blood clots to form.
These blood clots can detach from the heart, travel through the arteries to the brain, and lead to a stroke.
Other arrhythmias may occur in individuals with mitral valve reflux at the mitral valve.
endocarditis. Endocarditis is an inflammation of the inner lining of the heart (endocardium). Before surgical procedures (including on the teeth), doctors recommend taking antibiotics in patients with mitral valve regurgitation to prevent endocarditis.
pulmonary hypertension. In chronic and untreated mitral regurgitation, pulmonary hypertension can develop after many years. This disease consists in high arterial pressure in the lungs.
Diagnosis of mitral regurgitation
Since it is initially asymptomatic, the first sign the doctor notices may be a heart murmur.
The most common diagnostic examination methods are:
- Echocardiogram: this examination is an ultrasound of the heart and uses sound waves for visual representation. In echocardiography, the sound waves from a device (transducer) are directed at the heart. An echocardiogram allows the cardiologist to see the mitral valve well and assess how it works.
- Doppler sonography: provides color images (red, yellow and blue) of the venous and arterial bloodstream. Allows to detect a mitral return current and to see the extent.
- Electrocardiogram (ECG): used to record arrhythmias.
- Cardiac catheterization: to understand how serious the problem is and to detect coronary artery disease.
Quantifying the severity of mitral regurgitation
First degree (easy)
- The clinical picture, auscultation (eavesdropping), ECG and chest X-ray are normal.
- The sizes of the left atrium and ventricle are normal in the echocardiogram.
- percent of regurgitation < 20%.
- Mild heart failure is not a contraindication to sports.
Second degree (moderate)
- Possible deviations in medical history or physical examination, echocardiogram or X-ray horax.
- Slight enlargement of the left atrium and ventricle. Incomplete mitral valve closure according to the result of the color echo Doppler.
- percent of regurgitation 20-30%.
- Exercise is not contraindicated, but a control ECG should be performed annually to monitor the situation.
Third degree (moderate to severe)
- There are abnormalities in anamnesis, physical examination, echocardiogram or chest X-ray.
- Left atrium and ventricle are moderately to greatly enlarged.
- The left atrium is larger than the right atrium.
- Strong mitral regurgitation.
- Very clear incomplete closure of the mitral valve.
- percent of regurgitation between 30 and 40%.
Fourth degree (severe)
- There are heart problems in the anamnesis, physical examination, echocardiogram or X-ray horax.
- Complete absence of mitral valve closure.
- Premature closure of the aortic valve or reduced ejection fraction.
- Significant enlargement of the left ventricle and left atrium.
- Strong regurgitation flow that can be seen in the Doppler.
- percent of regurgitation > 40%.
Classification of mitral regurgitation according to the amount of blood flowed back
- Minimum < 30 ml/heartbeat
- Moderate 30-44 ml/heartbeat
- moderate-high 45-59 ml/heartbeat
- Highly ≥ 60 ml/heartbeat
Treatment of mitral regurgitation
Treatment for mild or asymptomatic chronic mitral regurgitation includes medications to prevent complications.
- Vasodilators, such as ACE inhibitors for elevated blood pressure.
- Diuretics used to treat symptoms of heart failure.
- Beta-blockers to lower blood pressure and heart rate.
Surgery may be needed to correct or replace the mitral valve if:
- symptoms of heart failure appear,
- the size of the left ventricle increases,
- the heart becomes weak.
With chronic regurgitation of the mitral valve, the doctor may order physical exercise or the reduction of salt in the diet.
Treatment of acute mitral regurgitation is carried out as an emergency in the hospital.
Surgical intervention is required to correct or replace the mitral valve.