Artificial Valves for Heart Valve Disease
Benefits of Mitral and Aortic Valve Replacement Surgery
Aug 26, 2009
Impaired function of the heart valves can lead to breathlessness, dizziness, chest pain and strain on the heart. In severe cases, valve replacement surgery is the only option.
The Valves of the Heart
The heart is essentially a muscular pump that contracts and relaxes continuously (the ‘heartbeat’) to drive blood around the body. Oxygen-carrying blood is pumped through the arteries from the lungs to the tissues, then oxygen-depleted blood is returned to the heart in the veins.
For this oxygen transport system to function properly, it is vital that the bloodstream flows in one direction only, and that oxygenated blood and deoxygenated blood are never allowed to mix. This is where the heart valves come in – by opening and closing in response to changes in pressure within the heart, these flaps prevent backflow, to keep the blood moving normally.
There are four valves in the heart, corresponding to its four chambers:
- mitral valve
- tricuspid valve
- aortic valve
- pulmonary valve.
Disorders of the Heart Valves
Heart valve disorders disrupt normal blood flow. There are two broad types of valve disease.
- In stenosis, the opening of a valve becomes narrowed, hindering the flow of blood. The narrowing may be congenital, or may be caused by rheumatic fever or by natural thickening of the valve that occurs with age.
- In regurgitation, blood leaks in the wrong direction through a valve. This may be due to infection or inflammation of the valve, or valve prolapse, in which the tissue of the valve becomes floppy.
Mitral valve stenosis, mitral valve regurgitation, aortic valve stenosis and aortic valve regurgitation are common types of heart valve disease. In some cases, these conditions can be managed with medications or by surgery to repair the damaged valve. In others, the only option is artificial heart valve replacement.
Types of Artificial Heart Valve
Two types of artificial valve are used for valve replacement – mechanical valves and tissue valves (or ‘bioprostheses’).
Mechanical valves come in various designs that control blood flow by means of a tilting disc, a caged ball or two rotating leaflets. They are made from carbon fibre, or from titanium with a carbon coating that reduces the risk of blood clots forming on the valve. The main advantage of a mechanical artificial valve is its durability; most will last for decades. However, people with a mechanical valve must take blood-thinning drugs for the rest of their life.
Bioprostheses are made from animal tissues – either pig heart valves, or tissues from the heart of a horse or cow sewn into a metal frame. These artificial valves do not last as long as mechanical valves and are therefore generally used in older people. Their main advantage is that blood-thinning drugs are needed only for the first few months after surgery.
Valve Replacement Surgery
Valve replacement is a major procedure requiring open heart surgery with cardiopulmonary bypass. While the heart is stopped, the diseased valve is removed and the artificial valve implanted in its place. The heart is then restarted and the blood allowed to flow.
Immediately after the procedure, patients are monitored closely in an intensive care unit. They can usually return home after one or two weeks, but full recovery can take several months, depending on how ill they were before the operation. People with a mechanical valve may be able to hear it clicking in their chest, but this is normal.
Outcome of Valve Replacement Surgery
Valve replacement carries the usual risks of major surgery, but the success rate is high. An artificial valve can be life-saving for people with severe heart valve disease. Most people with an artificial valve have a near-normal or normal life expectancy, and die of causes not related to valve disease. Regular follow-up is essential, however, to achieve the best results.
References
BUPA. Heart Valve Replacement Surgery. Accessed 26-08-09
Wheatley DJ. Valve Surgery. Medicine 2002; 30(5): 118–20.
Disclaimer
The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
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