- Mitral stenosis is a heart valve disorder.
- It commonly occurs in people who have a history of rheumatic fever.
- Symptoms are controllable to a point with medical treatment, but the condition is only correctible with surgery. Valvuloplasty is seldom done nowadays, as valve replacement has become the treatment of choice.
Mitral valve obstruction, mitral valve stenosis
What is mitral stenosis?
Mitral stenosis is the narrowing of the mitral valve. This n arrowing of the mitral valve prevents the left ventricle ( LV) from filling completely and results in a build-up of blood in the left atrium (LA) and eventually backwards into the lungs as well. This build-up can cause the LA to become stretched and can progress to Atrial Fibrillation (AF), an important rhythm disturbance.
What causes it?
Symptoms due to mitral stenosis most commonly occur in older people who have had rheumatic fever in childhood. Rheumatic fever can damage the valve in two ways:
- The leaflets of the valve may thicken, limiting its ability to open.
- The leaflets of the valve may fuse together, preventing it from closing properly which leads to regurgitation or "leaking".
The condition may very rarely be present at birth. Some babies are born with a narrowed mitral valve which develops into mitral stenosis early in life, while others are born with a malformed mitral valve putting them at risk of developing mitral stenosis with age.
What are the symptoms?
Symptoms will depend on how quickly the condition develops and how severe the stenosis becomes. Some people may never develop symptoms. However, mild problems may suddenly become worse.
Common symptoms are:
- Shortness of breath
- Frequent respiratory infections
- Heavy coughing , sometimes coughing up blood
- Chest discomfort or pain
- Heart palpitations
- Swelling of the feet or ankles
- Dizziness or fainting
How is it diagnosed?
The symptoms described by the patient will be very important and the diagnosis will be supported by a specific murmur, heard when the chest is examined. These heart murmurs vary in character, site and intensity, and provide much information on the state of the valve.
A chest x-ray will show whether there is enlargement of the heart or congestion of the lungs.
An ECG will give an overall indication of the state of the heart muscle and will also diagnose any rhythm disturbances, which are a common complication of valve disease.
The definitive investigation is the Echocardiogram. This is a "real-time" ultra-sound, which shows the heart contracting and the valves opening and closing as it happens. An external echocardiogram can be done in the cardiologist's rooms by a specially trained technician.
A far better and more accurate kind, however, is a Trans Esophageal Echocardiogram, or TEE. This is also a real-time ultrasound, but is done with the patient anaesthetized, via a special probe which the patient swallows very much like a gastroscopy. Very clear pictures and accurate measurements of blood flow and valve anatomy and function provide valuable information used in deciding on the best treatment for the patient.
An angiogram may be recommended to examine the state of the coronary arteries if the ECG indicates that there is concurrent arterial disease.
How is it treated?
Medical treatment is used to alleviate symptoms in patients whose valve problems are not yet serious enough to warrant surgery or for patients on whom for various reasons surgery is not possible.
Several important aspects are:
- Reducing the amount of fluid the heart has to pump, e.g. with diuretics (water-pills), to shed excess fluid and salt
- Slowing the heart rate, e.g. with beta blockers
- Keeping the blood pressure normal by means of various medications
- Anticoagulants very important in patients with rhythm disturbances like Atrial Fibrillation. In AF clots can form in the atrium, causing a stroke, heart attack or fatal pulmonary embolism. Anticoagulants such as Warfarin prevent these clots from forming.
Balloon valvuloplasty : a balloon-tipped catheter is introduced into the heart, much like an angiogram. When the balloon is situated within the narrowed valve, the balloon is inflated to stretch the valve open. Once this is achieved, the balloon is deflated and removed. Only certain types of valve problems can be handled in this way, and the procedure is seldom a permanent cure.
Surgery for valves can only be done with the patient on the bypass (heart-lung) machine, as the heart must be stopped and actually opened, so that the surgeon can work inside the heart.
Valve repair is not a satisfactory long-term option. Open-heart surgery to re-open the narrowed valve may give initial relief of symptoms, but the valve always re-narrows and the patient will need another operation (usually within ten years) to finally replace the valve.
Valve replacement is much more effective and can be done faster than a delicate repair procedure.
Different types of valves can be used. Mechanical valves are made of a virtually indestructible substance called Pyrolytic carbon. Provided they are correctly inserted, these valves can last the patient's lifetime. Because they are a foreign substance in the body and thus promote clot formation, the patient will need to use Warfarin anticoagulant permanently.
Bioprosthetic valves are harvested from cow or pig tissue and are treated to become inert (non-irritant). They thus do not tend to cause clot formation and the patient may not have to use Warfarin. The disadvantage of these valves is that they have a limited lifespan and may calcify after 10-15 years, and will therefore need to be replaced. If the patient has permanent AF, s/he will need to use Warfarin anyway, but may still receive a bioprosthesis for other reasons.
The timing of surgery is crucial. If valve replacement is delayed until the patient is in heart failure, the result will not be optimal and much of the lost cardiac function will not be restored.
What is the prognosis?
Valve surgery usually has an excellent outcome, especially if done by an experienced surgeon.
As time passes the body tries to re-line the valve with the same cells lining the inside of the heart.
Most valve replacements allow the patient to resume a near-normal life, with moderate exercise, etc. Attention to the need for anti-coagulation is vital, as is antibiotic prophylaxis. Other co-existing problems must also be managed.
Once a patient has had a valve replacement, s/he must be made aware of the need for antibiotic prophylaxis. This consists of a special type and dosage to be used before any surgical procedure, no matter how minor.
When to call your doctor?
Call your doctor if you experience symptoms such as persistent tiredness, cough, rhythm disturbances and shortness of breath these should immediately be investigated. Any chest discomfort especially if it occurs with exercise - is also significant.
How can it be prevented?
The most effective way to prevent mitral stenosis is to prevent its common cause, i.e. rheumatic fever, and to provide rapid, adequate treatment of diagnosed cases.
Eat less salt, do regular exercises, cut back on alcohol and manage hypertension.