Heart Valves: Function Repair & Replacement
Healthy valves are the heart's floodgates, opening to let blood transport oxygen and nutrients throughout the body and closing to make sure the blood flows in a forward direction. When these valves aren't working properly:
- Your heart may have to work harder to supply your body with life-giving blood.
- Backed-up blood may overfill your heart, enlarging it and making it weaker. Excess fluid in the heart can also harm your lungs.
The mitral valve is a one-way valve deep inside your heart that functions as a door between the left atrium and the left ventricle (the upper and lower left chambers of the heart). When the mitral valve is damaged or diseased it may impact the heart's ability to work efficiently, which can prevent normal blood flow from the heart to the body. Two major disorders cause most of the problems:
- Mitral valve prolapse, or regurgitation, happens when the valve leaflets (or doors) don't close properly, allowing blood to flow backward into the left atrium. This is the most common ailment of heart valves, affecting 2 percent of people in the United States.
- Mitral valve stenosis occurs when a narrowed valve opening forces your heart to work harder - though often unsuccessfully - to pump the same amount of blood out to your body. Twice as many women as men are affected.
Repair is preferred over replacement for mitral valve disorders because this preserves the valve and left ventricular function, eliminates risks associated with replacement valves, and does not require using anti-coagulants (blood-thinning medications) long-term. Repairs fall into three main categories:
- Commissurotomy - If the edges of the leaflets that form the opening of the valve are partially fused together, your surgeon will snip them apart to increase blood flow.
- Resection - The valve opening is surgically reshaped to restore its function or to remove extra tissue that is causing blood leakage.
- Annulus support - If the valve is too wide or too floppy, a soft, sturdy ring is sewn around the valve to tighten the opening and give it extra support.
If your mitral valve cannot be repaired, your surgeon will discuss valve replacement with you.
The aortic valve — keeping the blood flowing to your body
The aortic valve is located in the heart to regulate the main supply of blood to the body's major vessels. Two of the most common ailments of aortic valves are:
- Aortic stenosis, or narrowing of the aorta, which inhibits the forward flow of blood
- Aortic insufficiency, when the valve controlling blood flow doesn't close tightly, allowing blood to leak back toward the heart
Both of these conditions must be treated to prevent even more serious heart problems and weakening of the heart muscle. With an aortic valve problem, replacement is the preferred option.
Aortic valve stenosis and aortic valve insufficiency are generally caused by one of three conditions:
- Calcium buildup: Age is the main cause of this valve disorder. Blood contains calcium, a mineral, which over time, accumulates in hard deposits within the blood vessels and valves. The anatomy of the valve also makes it susceptible to calcium deposits.
- Heart defect from birth: A congenital defect, in which the valve has two leaflets instead of three, increases the risk for aortic valve stenosis. Also, a baby may be born with smaller valve openings. In this case, the surgeon may attempt a balloon valvuloplasty to enlarge the aortic valve opening.
- Rheumatic fever: One of the most serious side effects of rheumatic fever is its damage to the heart, specifically, the aortic valves. Although rheumatic fever is not as common as it once was, it still affects more than one million people in the U.S. and causes 6,000 American deaths per year.
There are two choices for valve replacement surgery: a mechanical valve or a biological valve. Each type of valve has its strengths and weaknesses, and your surgeon will work with you to help you decide which would be best for your particular circumstances:
- Mechanical valves are durable and designed to last a lifetime. They are often made of carbon, which is well tolerated by the body, and are covered in a polyester knit fabric that can be stitched to your own tissue. A drawback of mechanical valves is that patients will have to take anticoagulants for the rest of their life to prevent blood clots from forming on or near the mechanical valve. Younger patients may choose mechanical valves to avoid another operation 10-15 years down the road, though women who plan to get pregnant need to be aware that that they can't take some anticoagulants during the first and last trimesters of their pregnancy.
- Biological valves can be porcine (from pig tissue), bovine (from cow tissue) or from a human cadaver (allograft or homograft). Pig valves have been used for more than 30 years and have a proven track record. Cow valves have been used in the United States since 1991 and also have a good record for long-term durability. With biological valve replacement there is no need to take blood thinner medicine for the rest of your life. The disadvantage is its durability - a biological valve will generally need to be replaced after 10-15 years, depending upon the patient's age at valve implantation.
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