by Karen Schroeder, MS, RD, MEd
Anatomy and Physiology
The heart is a muscular organ that pumps blood through the body. It consists of four chambers. The upper chambers are the right and left atria. The lower chambers are the right and left ventricles. A muscular wall called the septum separates the right and left chambers. The chambers on the right pump blood to the lungs. The chambers on the left pump blood to the rest of the body.
The right and left atria, located in the upper chambers, connect to their respective ventricles in the lower chambers. The right ventricle connects to the pulmonary artery, and the left ventricle to the aorta. Valves are located at all of these connections to ensure that blood moves in only one direction.
The valves open to move blood forward and close to prevent blood from flowing backward. The parts of a valve that open and close are flaps of tissue called cusps. A tricuspid valve has three cusps and a bicuspid valve has two. The heart has four valves as shown here.
Blood flows in a continuous loop through the heart, lungs, and body tissues. Blood returning from the lungs is oxygen-rich and enters the left atrium. From here, the blood moves into the left ventricle through the mitral valve. When the heart contracts, the blood is forced through the aortic valve into the aorta where it is distributed to tissues throughout the body.
Oxygen-depleted blood returning from the body's tissues is collected in the right atrium. From there, it moves into the right ventricle through the tricuspid valve. When the heart contracts, the blood is forced through the pulmonary valve into the pulmonary artery where it is carried back to the lungs to be oxygenated again.
The aortic valve is located between the left ventricle and the aorta. When the heart contracts, the valve opens and blood is pumped into the aorta. When the heart relaxes, it closes to prevent blood from leaking back into the left ventricle. A normal aortic valve has three smooth cusps that open widely and close tightly.
Reasons for Procedure
When the aortic valve is not functioning properly, blood flow is disrupted and the heart must work harder. The aortic valve can be faulty in two main ways: leaky, or regurgitant, narrowed, or stenoticA leaky valve does not close all the way. Therefore, between each heartbeat, the blood leaks back into the ventricle. This is called aortic regurgitation.
A constricted aortic valve does not open all the way. The opening is narrow, so less blood can pass out of the ventricle and into the aorta. This is called aortic stenosis.
A person may be born with an abnormal aortic valve. This is called a congenital defect. For example, the aortic valve may have only two cusps instead of three, and therefore, may not open and close properly. People may live with an abnormal, bicuspid valve for years before symptoms occur.
An aortic valve may also become damaged during life. This is called acquired aortic valve disease. Causes include: rheumatic fever, which can be a complication of untreated strep throat; endocarditis, which is a bacterial infection of the valve; sclerosis, or hardening of the aortic leaflets.
After a period of time, a faulty valve can cause the heart muscles to become enlarged and weakened. Depending on the nature of the valve's defect, the walls of the left ventricle may become abnormally thick or thin, and the problem can eventually affect the right side of the heart as well. Patients with this condition, known as heart failure, may experience: shortness of breath, chest pain, or angina pectoris, dizziness, lightheadedness, and/or fainting, swelling of the ankles, feet, and legs, and/or fatigue.
Many patients with defective or damaged aortic valves may be treated with medications to reduce the workload of the heart, lower high blood pressure, or prevent abnormal heart rhythms. There are no medications, however, to restore the valve to normal. Close monitoring is essential, to determine when repair or replacement of the valve becomes necessary.
Your doctors will determine the best treatment based on your medical history, physical examination, and tests to assess your heart's function. These tests may include: chest x-ray, to evaluate the size of the heart and check for any fluid in the lungs, electrocardiogram, or EKG, which measures the electrical activity of the heart, echocardiogram, which uses high-pitched sound waves to create images of the beating heart's chambers and valves, cardiac catheterization, which involves the placement of a catheter in the heart to evaluate its blood supply and function. In most cases, a damaged aortic valve-whether stenotic or leaky-will eventually need to be replaced. There are two types of replacement valves: mechanical valves - made from metal, carbon, or other harmless materials, one example is the St. Jude valve and tissue valves - donated from humans or animals.
There are three main types of tissue valves: Xenograft or bioprosthetic valves from animals, usually a pig or cow, Homograft or allograft valves from human donors after death, pulmonary autograft valves, in which the aortic valve is replaced with the patient's own pulmonary valve, and the pulmonary valve is replaced with a human donor valve; this is called a Ross procedure.
In the weeks leading up to your procedure: if you smoke, stop. Smoking increases your risk of complications; obtain dental clearance from your dentist; if you regularly take medications, herbs, or dietary supplements, your doctor may ask you to temporarily discontinue them. This is especially true of medications that thin the blood, such as aspirin or warfarin. Do not start taking any new medication, herbs, or dietary supplements without consulting your doctor. Arrange for a ride to and from the hospital, and for help at home as you recover. Eat a light meal the night before. Do not eat or drink anything after midnight.
In preparation for your surgery, once you arrive at the hospital you will receive: an IV line in your arm to provide fluids and medications, other lines and monitors to track your vital functions, a catheter in your bladder to drain urine.
Aortic valve replacements are done under general anesthesia. This means you will be asleep for the duration of the operation, and a tube will be placed through your mouth and into your windpipe to help you breath during surgery.
Once the anesthesia takes effect, your surgeon will begin by making an incision in the chest. The traditional incision is 6-8 inches in the middle of the chest overlying the breastbone, or sternum. In some cases, such as in patients who have coronary artery disease, a smaller, partial incision is made. The surgeon then separates the sternum to expose the pericardium, which is a protectivemembrane encircling the heart.
Your surgeon will then open the pericardium to expose the heart. At this point, your heart will be connected to a heart-lung machine. Tubes are used to reroute your blood into this machine, which takes over the functions of the heart and lungs during the operation. Once the heart-lung machine has taken over, your heart will be temporarily stopped and the blood inside removed. This keeps the aortic valve still and allows your surgeon to see it.
Your surgeon will open the aorta to expose the aortic valve, make an incision around the edge of the damaged valve, and remove it. Your surgeon will then carefully sew the replacement valve into place and close the aorta with stitches.
At this point, blood will again be allowed to flow into your heart to check the function of the new valve. If needed, an electric shock will be given to restart the heart. Once your heart is beating on its own, it will be detached from the heart-lung machine.
For a pulmonary autograft, or Ross procedure, your surgeon will begin by examining the aortic and pulmonary valves to determine if this procedure will work. If so, your surgeon will first remove both the diseased aortic and healthy pulmonary valves. He or she will then sew the pulmonary valve in place of the aortic valve. Finally, your surgeon will replace the pulmonary valve with a valve from a human donor.
Once the valve is in place and has been tested, all the incisions will be closed. Generally, temporary pacemaker wires are placed on the surface of the heart to ensure the heart maintains a normal rhythm during recovery. Aortic valve replacements usually take about four hours. Ross procedures take a bit longer.
Risks and Benefits
Risks of aortic valve replacement are similar to other open-heart surgical procedures. They include: bleeding, infection, difficulty breathing, heart rhythm problem requiring permanent pacemaker, temporary confusion due to the heart-lung machine, heart attack, stroke, kidney failure, adverse reactions to anesthesia, and/or death.
Mechanical valves are very durable and should last a lifetime. However, they increase the risk of blood clots, which can lead to a stroke or other serious conditions. To reduce this risk, you will need to take blood-thinning medication for the rest of your life. This medication will slightly increase your risk of bleeding complications in the future.
The risk of blood clots is much lower with tissue valves, which do not require you to take blood-thinning medication over the long term. However, tissue valves are less durable than the mechanical valves, and may need to be replaced in 10-15 years.
The Ross procedure can be beneficial because the new valves generally last a long time, perhaps a lifetime. However, the surgery is longer and more difficult, and there is a small risk of leakage at the aortic valve site, requiring another surgery.
The major benefit of any aortic valve replacement is that it removes the cause of debilitating symptoms and prevents worsening heart failure. Once surgical wounds have healed, most people have very few or no restrictions in their activity.
In an aortic valve replacement, or any other procedure, you and your doctor must carefully weigh the risks and benefits to determine whether it's the most appropriate treatment choice for you.
After the Procedure
After surgery, you'll be taken to the intensive care unit where multiple wires will connect you to devices that closely monitor your vital functions. You will still have a breathing tube in your throat, which will prevent you from talking. Several tubes will be in place to drain blood and fluid from your incision, and your bladder catheter will still be draining your urine.
You'll be given pain medication and asked to take frequent deep breaths and periodically cough to keep your lungs well inflated. You will also be encouraged to move your legs to help prevent blood clots from forming in your veins. In 1-2 days, you can expect to leave the ICU and move to a regular floor. Most patients are discharged home in 5-6 days.
Prior to discharge, the hospital staff will help you arrange home care, if necessary, and schedule follow-up appointments with your doctor. They will also help you get started on activities to aid your recovery at home. These include: care and cleaning of your incision, walking and other gentle exercises, taking your medications on schedule, monitoring your fluid balance by weighing yourself daily, following nutrition guidelines, such as limiting salt and keeping weight in a healthy range. You may be prescribed a blood thinner, such as CoumadinÂ®, which will require monitoring with periodic blood tests. If you have a tissue valve, you will likely take this drug for at least six weeks. With a mechanical valve, you will take it for the rest of your life. It will be important to limit your activity as you recover. For example, do not lift anything heavier than ten pounds for three months. Complete recovery may take 4-6 months.
Call your doctor promptly if you experience any of the following: chest pain, heart palpitations, or shortness of breath, lightheadedness or fainting, weight gain of three pounds or more in one day, signs of infection, such as fever and chills, warmth, redness, or swelling around your incision, bleeding or other fluid drainage from your incision. If you are taking a blood-thinning drug, call your doctor if you experience any of the following: a serious fall or blow to your head, excessive bruising on your skin, excessive bleeding, such as nose bleeds or bleeding gums, blood in your urine or stool, a fever or other illness, including vomiting or diarrhea.
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Available at: http://www.debakeydepartmentofsurgery.org/home/content.cfm?proc_name=aortic+valve+replacement&content_id=274 Accessed October 4, 2004.
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Available at:http://www.mayoclinic.org/aorticregurgitation-jax/ Accessed October 4, 2004.
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Available at: http://www.sts.org/doc/3620 Accessed October 4, 2004.
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Available at: http://www.sjm.com/procedures/procedure.aspx?name=Heart+Valve+Replacement Accessed October 4, 2004.
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Available at: http://www.nlm.nih.gov/medlineplus/ency/article/002954.htm Accessed October 6, 2004.
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