Mitral stenosis: causes, symptoms, monitoring and treatment

The heart has four valves that act like one-way doors. The mitral valve sits on the left side, between the upper chamber (the left atrium) and the lower chamber that does most of the pumping (the left ventricle). The British Heart Foundation explains that valves have small flaps, called leaflets or cusps, that open and close with every heartbeat to stop blood flowing backwards.

In stenosis the flaps become thick, stiff or calcified, so the opening is smaller than it should be. The NHS groups this under heart valve disease and describes stenosis as a valve that does not open fully, which means the heart has to work harder to pump blood around the body. Problems with the mitral and aortic valves are the most common types.

Because the narrowed opening holds blood back, the upper chamber works against resistance and can enlarge over time. That is the background to the rhythm problems and breathlessness that some people eventually notice.

The Leeds patient information names rheumatic fever as the most common cause and suggests that a prolonged feverish illness in childhood or youth may be relevant to the story. Rheumatic fever is an inflammatory reaction that can follow a throat infection and can leave scarring on the valves; it is now uncommon among people who grew up in the UK but remains a leading cause of valve damage in many other parts of the world.

Other causes in the same leaflet are age-related degeneration of the valve ("wear and tear") and being born with an abnormal valve. The NHS page on heart valve disease adds that valve problems in general can follow changes to the heart with age, particularly with smoking, high blood pressure or high cholesterol, and can follow conditions such as rheumatic fever, cardiomyopathy or endocarditis.

• Rheumatic fever earlier in life (often the explanation for narrowing in younger and middle-aged adults).

• Age-related thickening and calcium build-up on the valve.

• A valve that was abnormal from birth.

If the narrowing is mild there may be no symptoms at all. When symptoms do appear, the NHS list for heart valve disease includes shortness of breath, tiredness or weakness, dizziness, palpitations, swollen ankles and feet, and chest pain or discomfort. Some people only find out because a doctor hears a murmur, the sound blood makes as it passes through a thickened or leaking valve.

For people already known to have mitral stenosis, the Leeds leaflet singles out four changes to tell the valve team about between appointments: increasing breathlessness (especially on exertion or when lying flat), palpitations such as a rapid or irregular heartbeat, difficulty exercising, and unexplained sweats or fever. The sweats or fever point matters because abnormal valves can become infected.

A GP will usually listen to the heart first and may arrange tests or refer you to a cardiologist. The NHS lists an echocardiogram, a chest X-ray and an ECG as typical first tests. The British Heart Foundation calls the echocardiogram the most common test used to diagnose heart valve disease, and says other tests can include blood tests, cardiac CT, cardiac MRI and an angiogram.

The Leeds leaflet explains that mitral stenosis is graded as mild, moderate or severe. A transoesophageal echocardiogram (TOE) is a day-case test done under sedation, a little like an endoscopy, in which a probe is passed into the gullet to get close-up ultrasound pictures of the heart. An angiogram is an X-ray dye test of the heart arteries done under local anaesthetic. Both tend to be used when a procedure is being planned rather than for every patient.

For many people the plan is observation. The Leeds leaflet says that whatever the severity, someone without symptoms will probably be reviewed with intermittent clinic visits and echocardiograms because the valve disease can progress, and that mild disease usually needs only very occasional monitoring. The British Heart Foundation gives general intervals for heart valve disease: mild disease without symptoms might be checked every 3 to 5 years, while moderate or severe disease without symptoms is usually checked every 6 to 12 months. Your own team sets the schedule that fits your valve.

Medicines cannot reopen a narrowed valve, but they can ease symptoms or reduce complications. The NHS describes medicines in heart valve disease such as ACE inhibitors, diuretics (to reduce fluid build-up), drugs to slow the heart rate and anticoagulants to reduce the risk of blood clots. Which of these applies depends on symptoms and on whether an irregular rhythm is present, so it is a decision for the treating cardiology team.

If the stenosis becomes severe and causes symptoms, or the heart becomes stretched or weakened, the Leeds leaflet says referral for a procedure may follow after a series of tests to decide what suits you. The two options it describes are surgical replacement, with a tissue or mechanical valve, and a percutaneous (keyhole) balloon procedure in which a balloon is inflated inside the valve to improve how well the leaflets move and the valve opens, done under general anaesthetic. The NHS notes that heart valve surgery can either repair a valve or replace it with an artificial valve or one made from human or animal tissue.

General heart-healthy habits are encouraged: the Leeds leaflet recommends a healthy diet, keeping weight in the normal range and stopping smoking, with support available through the GP. It says most people face no limit on exercise, though this is worth confirming with the care team. The British Heart Foundation adds that people with heart valve disease may need to avoid straining or holding their breath, for example heavy lifting, and that advice changes if breathlessness develops.

Dental health has a specific role. The Leeds leaflet explains that bacteria from the mouth or skin can reach abnormal valves and cause an infection called endocarditis, so it recommends brushing twice a day, seeing a dentist at least once a year, getting toothache or abscesses treated quickly and telling the dentist about the valve condition.

Pregnancy needs planning. Both the NHS and the Leeds leaflet say to discuss it with a healthcare professional before conceiving, since pregnancy can make valve symptoms worse and may need extra monitoring and treatment.

Diagnosis and long-term valve surveillance are normally organised through a GP referral to an NHS cardiology or heart valve service, often with a named valve nurse. Private cardiology can offer echocardiography and specialist opinions, but decisions about balloon treatment or surgery are usually made by a multidisciplinary valve team, and records and scans can be shared between services. Prices, waiting times and which procedures a hospital performs vary, so ask any provider for an itemised explanation.