It is an obstruction of the mitral valve (the heart valve that separates the left atrium from the left ventricle).
Mitral valve stenosis prevents the mitral valve from opening properly, in some cases by causing the two flaps to partially fuse.
When this mitral valve is constricted, blood flow from the left atrium to the left ventricle is reduced and this prevents some of the blood from leaving the atrium.
Mitral stenosis is relatively rare today in developed countries, but when it occurs it can cause significant heart problems.
Mitral valve function
The mitral valve is located between the upper left chamber of the heart (the left atrium) and the lower left chamber of the heart (the left ventricle).
It opens to allow blood to move out of the atrium into the ventricle and then closes to prevent blood from moving in the wrong direction.
When a heart with a healthy mitral valve contracts, it sends blood from the atrium to the empty left ventricle.
The two flaps of the mitral valve open to allow blood to pass through. When the heart relaxes and the ventricle fills with blood, the flaps close.
Once the left ventricle is filled, it contracts to pump blood out to the body, and the mitral valve closes to prevent blood from returning to the left atrium.
With mitral stenosis, the mitral valve becomes thicker and immobile (that is, stenotic) and can no longer open fully.
When this happens, the left atrium cannot completely empty into the left ventricle.
Incomplete emptying produces an increase in left atrial pressure. Over a long period of time, significant heart problems can arise.
Causes of mitral stenosis
Several conditions can cause mitral stenosis:
- Rheumatic heart disease is the most common cause of mitral stenosis. Because rheumatic heart disease has become rare in developed countries, mitral stenosis is now seen much less frequently than in past decades.
- Some forms of congenital heart disease can cause mitral stenosis. In these cases, the mitral valve does not develop normally.
- Mitral annulus calcification (a condition in which calcium deposits form on the mitral valve. As you age, calcium can accumulate around the valve, leading to a variety of complications. It is a fairly common condition, most often causing mitral regurgitation and rarely leading to mitral stenosis.
- The endocarditis infectious (infection of the heart valves) can rarely cause mitral stenosis.
- Mitral valve stenosis can also be caused by rheumatic fever , a childhood illness that occurs along with conditions such as strep throat or scarlet fever. Complications from these conditions can damage the mitral valve or even cause it to fuse, although symptoms may not appear until years later. Although extremely rare due to effective antibiotics, rheumatic fever is still the second leading cause of mitral valve stenosis.
Other causes of mitral stenosis include:
- Prior external radiation to the chest cavity during cancer treatment can occasionally produce mitral stenosis a decade or two after treatment, especially after treatment for Hodgkin lymphoma.
- Previous known history of congenital or birth-related abnormalities.
- Some rare medications.
In mitral stenosis caused by rheumatic heart disease (the most common cause), the valve problem develops slowly, over a period of years, and symptoms appear gradually.
In most cases, mitral stenosis is first diagnosed 15 to 20 years after rheumatic fever has occurred.
During this period of time, the pressure within the left atrium gradually increases, causing that chamber to eventually enlarge.
The increased pressure is also transmitted backward, to the blood vessels in the lungs, and eventually to the pulmonary artery. Which often results in pulmonary artery hypertension, or high pressure in the pulmonary artery.
Pulmonary artery hypertension can eventually cause heart failure that affects the right side of the heart.
Right heart failure is commonly associated with extreme fatigue and massive fluid buildup (edema) in the legs and often in the abdomen.
Atrial fibrillation is very common in people with mitral stenosis. Up to 70% of people with mitral stenosis will develop this arrhythmia.
Thromboembolism is also a problem with mitral stenosis. Blood clots that form inside the abnormal left atrium rupture and cause tissue damage, especially a stroke.
This problem is a risk for anyone with atrial fibrillation, but that risk is especially high when atrial fibrillation is associated with mitral stenosis. In fact, thromboembolism can occur with mitral stenosis even in the absence of atrial fibrillation.
The most common symptoms caused by mitral stenosis are dyspnea (shortness of breath), cough, and fatigue.
People with mitral stenosis are more likely to experience these symptoms whenever the heart is asked to do a little more work, such as during exercise of any kind, emotional stress, fever, or other illness or pregnancy.
Just as mitral stenosis itself develops very gradually, so do the symptoms it causes.
In many cases, people with mitral stenosis avoid symptoms by unconsciously reducing their activity level over a period of years and eventually becoming quite sedentary.
Because they are so inactive, they will often not notice the breathing problem and may not report this symptom to their doctors.
When mitral stenosis worsens, patients can develop persistent symptoms even at rest, and they can also develop severe edema and start coughing up blood.
Atrial fibrillation can cause palpitations and dizziness, and can worsen all the symptoms associated with mitral stenosis.
Diagnosis of mitral stenosis
The diagnosis is often first suspected after the doctor performs a physical exam and notices the soft, rumbling heart murmur that is characteristic of mitral stenosis.
Once the diagnosis is suspected, it can be easily confirmed or ruled out with a variety of diagnostic tools.
The main diagnostic imaging method for determining mitral stenosis is echocarciography.
While echocardiography provides information on the mitral valve area, the size and function of the left atrium and ventricle, and the presence of thrombus, the Doppler examination provides information on the complexity of the stenosis.
Transoesophageal echocardiography is used when the valve cannot be evaluated with transthoracic echocardiography. This method is also useful to determine the presence of intracardiac thrombi before surgery.
Mitral stenosis treatment
If you have been diagnosed with mitral stenosis, the most important thing for you and your doctor to consider is whether or not to perform a surgical procedure to relieve the stenosis and what steps should be taken to prevent thrombosis.
Management of mitral stenosis during pregnancy
One of the biggest challenges in mitral stenosis is proper management and therapy, and patients with moderate or severe mitral stenosis should be monitored during pregnancy.
Cardiovascular changes in pregnancy can contribute to maternal, fetal, and neonatal complications.
Pregnancy in women with mitral stenosis requires precise planning to avoid possible complications, which can be fatal.
For the best result, a multidisciplinary approach is necessary during pregnancy. In addition, prenatal management is very important to avoid cardiac decompensation.
The fetus is also affected and there is a risk of premature delivery and intrauterine growth retardation.
The main goal of management is to reduce the heart rate. Pregnancy carries risks and complications for patients with mitral stenosis.
Medications for mitral stenosis are not highly recommended in pregnancy.
Therapy is symptomatic, activity must be restricted. Selective β-1 blockers are used, and diuretics can be used if symptoms persist.
Women with moderate or severe mitral stenosis, large left atrium, low cardiac output, or congestive heart failure are at high risk of thromboembolism. That is why anticoagulant drugs are used in therapy.
Delivery should be vaginal in patients with mild or moderate and severe mitral stenosis who do not have pulmonary hypertension, while cesarean section is considered in those patients with moderate and severe mitral stenosis or pulmonary hypertension.
Complications of mitral valve stenosis
Without treatment, mitral valve stenosis can lead to:
- Heart failure: a condition in which your heart cannot pump enough blood to meet the needs of your body.
- Enlargement of the heart.
- Atrial fibrillation
- Blood clots (atrial fibrillation increases the risk of developing blood clots).
- Accumulation of fluid in the lungs.
Complications such as pulmonary edema and arrhythmias occur in 35% of pregnancies, while the incidence of other maternal cardiac complications correlates with the severity of mitral stenosis.
In pregnancy, the heart rate increases, therefore the left atrial and pulmonary pressure increases.
During the second or third trimester, in pregnant women with mitral valve stenosis, cardiac decompensation and pulmonary edema may occur, while the risk of maternal death is higher during delivery or during the immediate postpartum period.
Autotransfusion of the uterus can flood the central circulation, which can lead to severe pulmonary edema. The risk of pulmonary edema continues for several days after delivery, because autotransfusion of blood can last 24 to 72 hours after delivery occurs.
The mortality rate varies, where for mild mitral stenosis it is greater than 1%, while for moderate to severe mitral stenosis it ranges between 5 and 15%.
The worst outcome in pregnant patients with mitral stenosis is miscarriage.
Mitral stenosis is also seen along with the main congenital aortic stenosis and coarctation lesions.
Pulmonary hypertension can develop during pregnancy, as a result of mitral stenosis.
In patients with mild to moderate mitral stenosis during pregnancy, an increase in the diameter of the left atrium and a significant decrease in the diameter of the left atrium have been reported after delivery.