The mitral valve is a flap-like structure made of two leaflets - anterior leaflet and posterior leaflet, located between the left heart chambers. It functions like a one-way door for the blood to flow from the left atrium into the left ventricle, then further across the aortic valve into the aorta supplying down to the entire body.

By Dr Zhu Ling, Associate Consultant, Department of Cardiothoracic Surgery

Mitral valve disease occurs when the mitral valve does not function properly. Forms of the disease include regurgitation (leakage), when the mitral valve leaflets are not able to close tightly, causing blood to leak back from the left ventricle into the left atrium; and stenosis when the mitral valve leaflets thickened or become stiff and fuse together, narrowing the valve opening resulting in inadequate blood flow from the left atrium into the left ventricle.

Causes and Complications

Mitral valve disease has many causes. Some forms can be already present at birth (congenital heart defect), while more commonly seen forms are developed later in life or acquired. The most common cause of mitral valve stenosis is rheumatic heart disease, where an infection (rheumatic fever) causes the heart to become inflamed. Mitral valve regurgitation, on the other hand, can be caused by mitral valve prolapse (floppy valve), endocarditis (infection), heart attack, or autoimmune disease such as lupus disease.

If left untreated, mitral valve disease can lead to serious, life-threatening complications such as heart failure, irregular and often rapid heart rate, blood clots and stroke.

Diagnosing Mitral Valve Disease

Some patients can be symptom-free for many years even with serious mitral valve problems. Otherwise, signs and symptoms of mitral valve disease include fatigue, decrease in effort tolerance, heart murmur, palpitation, irregular heartbeat, and shortness of breath even at rest.

When diagnosing mitral valve disease, a cardiologist will require a thorough medical history, detailed physical examination and if required, investigations may include:

• Echocardiogram: an ultrasound scan of the heart that provides details of the heart structures and function, is usually performed over the chest (known as a transthoracic echocardiogram). In certain cases, the ultrasound is done via a probe inserted into the food pipe (transoesophageal echocardiogram) to get a closer look at the heart, especially at the mitral valve (from the back of the heart).

• Electrocardiogram (ECG): detects enlarged chambers of the heart, heart disease and irregular heart rhythms.

• Chest X-ray: provides information for both the heart and lungs.

• Cardiac magnetic resonance imaging (MRI): produces extra information of the heart chamber and valve condition.

• Exercise tests or stress tests: help reveal how the heart responds to physical activity and whether valve disease symptoms occur during exercise. These tests often involve walking on a treadmill or riding a stationary bike.

• Cardiac catheterisation: checks on the heart vessel conditions via a procedure in which a thin, flexible tube is guided through a blood vessel to the heart. Coronary bypass surgery may sometimes be carried out at the same time with valve surgery if there is serious blockage of the heart vessel.
  
  

Treatment – Intervention, Repair or Replacement

Mitral valve disease treatment depends on the symptoms, the severity of the condition, and the progress of the disease. Options may include monitoring the condition with regular follow-up visits, medications for the symptoms and medical interventions.

Percutaneous Intervention

Percutaneous intervention of the mitral valve is done in the cardiac catheterisation lab by the structural heart team. Commonly performed procedures include:

• Valvuloplasty for the narrowed mitral valve (mitral stenosis) - a catheter with a balloon on the tip is inserted through the groin vessel and threaded up to the mitral valve. The balloon is then inflated and the opening of the mitral valve is widened. The procedure can be performed even when the patient is symptomfree with a severely stenosed valve.

• MitraClip for a leaking mitral valve (mitral regurgitation) - a catheter with a clip on its end is guided to the mitral valve through the groin vessel. The clip is then anchored onto a torn or leaky mitral valve leaflet. This procedure serves as an option for patients with severe mitral regurgitation, particularly for those who are at high risk for mitral valve surgery.

• In some cases, a heart catheter procedure may also be done to insert a replacement valve into a biological tissue valve that is no longer working properly, known as a valve-in-valve procedure.
  

• Removing the excess tissue so the leaflets can close tightly (resection of part of the valve)

• Replacing the supporting structure (chords) of the mitral valve

• Patching the holes in the heart valve leaflets (patch repair)

• Splitting the valve leaflets that have fused (commissurotomy)

• Tightening or reinforcing the ring around the valve (annuloplasty)
  
  

Mitral Valve Replacement

In certain cases, when the mitral valve condition is not amenable to repair, the diseased mitral valve has to be replaced, that is, to change a new one. During mitral valve replacement, the original mitral valve tissue is removed, after which a new valve (using a mechanical valve or a tissue valve made from cow, pig or human heart tissue) will be implanted.

For a mechanical valve, the patient has to take a life-long strong blood thinner (warfarin) to prevent clots on the valve. They will need to take blood tests regularly to monitor the effect of the blood thinner and take precautions to prevent excessive bleeding. With good care, a mechanical valve can last a lifetime and does not usually wear out.

A tissue valve, on the other hand, does not need life-long warfarin, although the patient may require blood thinning for other conditions such as chronic atrial fibrillation (or irregular heartbeat). Tissue valve can break down over time, with wear and tear or calcium deposition. There may be a need for re-intervention after 10 to 15 years, in which case, another operation or percutaneous intervention may be needed.

Conclusion

Mitral valve disease is not an uncommon disease in Singapore. Patients with mitral valve disease need to work closely with their cardiologist and cardiac surgeons to manage their symptoms and prevent complications. With early diagnosis, proper treatment and management, and lifestyle changes, patients with mitral valve disease may still lead a normal life.

This article is from Murmurs Issue 44 (September – December 2022). Click here to read other articles or issues.