Sometimes a natural heart valve that is not working properly needs to be replaced surgically with a prosthetic valve. A prosthetic valve is a synthetic or tissue substitute for the natural valve. It is designed to mimic the natural valve's normal opening and closing motions. A prosthetic valve can replace any of the three heart valves -- aortic, pulmonary or tricuspid. Prosthetic heart valves are divided into two basic categories: synthetic mechanical valves and biological valves made of human or animal tissue.
Several different forms of mechanical valves have been approved by the U.S. Food and Drug Administration (FDA) for use in hospitals in the United States. The different types vary in the mechanisms they use to open and close the valves.
In general, mechanical valves tend to last longer than biological valves, but they also carry a greater long-term risk of thromboembolism, which is a floating blood clot that can travel through the circulation, causing stroke and other problems. To help prevent thromboembolism, people who receive mechanical heart valves must take anticoagulant medications (anticlotting drugs) for the rest of their lives. However, this long-term use of anticoagulants also increases the risk of bleeding problems.
Although mechanical valves generally are used in younger patients because of their durability, the need for anticoagulant medication can complicate a pregnancy in young women.
Biological valves can be made of either human or animal tissue. Options include:
- Autograft valves. In this case, the replacement valve is made from another valve within the patient's own heart. For example, the patient's pulmonary valve may be removed and used to fix the aortic valve. The missing pulmonary valve is then replaced by one of the other options.
- Homograft valves. This replacement valve is taken from a deceased human donor.
- Heterograft valves. In this case, the replacement valve comes from an animal donor, either a pig or a cow.
In general, biological valves are less durable than mechanical valves. They are more likely to wear out and need to be replaced. Because they are more likely to wear out, biological valves are used more often in people aged 65 to 70 or older because their expected lifespan is shorter. Since the long-term risk of thromboembolism is lower for biological valves than for mechanical valves, the patient doesn't normally need to take anticoagulants for more than three months after surgery. Therefore, many younger patients who have active lifestyles and do not want to take anticoagulants choose to use biological valves.
Currently, 71,000 to 79,000 heart valve replacements are done each year in the United States.
The reasons for a heart valve replacement vary slightly, depending on which of the four heart valves is involved. As a general guide, however, you may need a valve replacement for any of the following reasons:
- You have significant valve narrowing (stenosis) or leaking (regurgitation) that is causing severe cardiac symptoms, such as angina (chest pain), shortness of breath, syncope (fainting spells) or symptoms of heart failure.
- Although your cardiac symptoms are not yet severe, diagnostic tests show that you have valve stenosis or regurgitation that is beginning to seriously affect your heart function.
- You have milder valve stenosis or regurgitation, but you need open heart surgery for another reason (such as coronary artery bypass). Your problematic heart valve can be replaced during this open heart procedure, correcting the situation before it has the chance to deteriorate.
- Your heart valve has been damaged severely by endocarditis (infection of the heart valve), or you have endocarditis that is resistant to antibiotics.
- You already have a prosthetic heart valve, but it needs to be replaced because it is leaking or malfunctioning, because you are having recurring blood clots or infection on the heart valve, or because you are having bleeding problems related to anticoagulants.
Your preparation will include a thorough cardiac evaluation with a physical examination, chest X-ray, electrocardiogram (EKG) and echocardiography. In some cases, exercise testing, cardiac catheterization or a cardiac magnetic resonance imaging (MRI) scan may be necessary as well. Routine blood tests also will be done to evaluate your kidney function and to check for anemia and other blood-related problems.
An intravenous (IV) line will be inserted into your arm to deliver fluids and medications, and you will be given general anesthesia. With traditional heart valve surgery, a large incision will be made in the midline of your chest. The surgeon will need to cut through your breastbone to expose the heart. After your heart is exposed, you will be placed on a heart-lung machine, a machine that oxygenates and pumps your blood during surgery. Your heart will be cooled and stopped temporarily. Once your heart is motionless, the surgeon will cut through its muscular wall to remove the malfunctioning heart valve, insert the prosthetic valve, and stitch it into place.
After closing the incision in your heart wall, the surgeon will begin to warm your heart. If your heart does not start to beat again on its own after it has returned to normal temperature, the surgeon may need to trigger the heartbeat with an electric shock. Once it is clear that your heart is pumping steadily without leaking blood, you will be disconnected from the heart-lung machine. The surgeon will use wires to reattach the halves of your breastbone, your chest incision will be stitched closed, and you will be taken to the cardiac surgical intensive care unit.
For some patients, the heart surgeon is able to repair or replace a heart valve through a smaller incision.
After one or two days in the cardiac surgical intensive care unit, you will be transferred to a regular hospital room. There you will continue to be monitored with daily blood tests and EKGs until you are stable enough to go home. Depending on your doctor's routine treatment strategy, you may either have another echocardiogram before you are discharged from the hospital, or you will have one as an outpatient.
New technologies allow artificial valves to be inserted into the heart via special catheters, without opening the patient's chest. Heart specialists are gaining more experience with this approach. Currently, heart surgery through an incision is usually the better choice for people at low or average surgical risk.
After your heart valve replacement, you will need to take anticoagulant medication indefinitely if you have a mechanical valve, or for about three months if you have a biological valve. Your doctor, or your doctor's assistant, will work with you to determine an anticoagulant dose that is high enough to prevent thromboembolism but low enough to prevent bleeding problems. Also, for the rest of your life you will need to take antibiotics prior to having certain high-risk dental or medical procedures. These antibiotics will help to prevent infection of your prosthetic valve, if the high-risk procedure allows bacteria to stray into your bloodstream.
After discharge, your doctor will ask you to return for a follow-up visit within 3 to 4 weeks. If you are feeling well at that visit, and the results of your repeat echocardiography are good, your doctor will schedule future visits at 3-month or 12-month intervals.
Mechanical heart valves that have been approved by the FDA rarely fail. However, even when patients take enough anticoagulants, a small number develop blood clots on the valves. Each year, 1.3% to 2.7% of patients who have a mechanical heart valve experience an episode of severe bleeding related to anticoagulants.
Biological valves tend to fail over time -- requiring replacement in 30% of patients within 10 years and 50% within 15 years. However, the risk of blood clots is very low.
After your discharge, call your doctor immediately if:
- You develop chest pain, shortness of breath, dizziness or an irregular heartbeat
- You have a fever
- Your incision becomes red, swollen and painful, or it oozes blood
National Heart, Lung, and Blood Institute (NHLBI)
P.O. Box 30105
Bethesda, MD 20824-0105
American Heart Association (AHA)
7272 Greenville Ave.
Dallas, TX 75231