Mitral Valve Replacement
Mitral valve replacement is a cardiac surgery procedure in which a patient’s mitral valve is replaced by a different valve. Mitral valve replacement is typically performed robotically or manually, when the valve becomes too tight (mitral valve stenosis) for blood to flow into the left ventricle, or too loose (mitral valve regurgitation) in which case blood can leak into the left atrium and back up into the lung[1]. Some individuals have a combination of mitral valve stenosis and mitral valve regurgitation or simply one or the other.
A mitral valve replacement/repair is performed to treat severe cases of mitral valve prolapse, heart valve stenosis, or other valvular diseases.[2] Since a mitral valve replacement is an open heart surgical procedure, it requires placing the patient on cardiopulmonary bypass to stop blood flow through the heart when it is opened up[1].
A mitral valve replacement is necessary when the valve doesn’t open or close completely. When the valve narrows or is stenotic the valve doesn’t let blood flow easily into the heart causing the blood to "back up" and pressure to build up in the lungs[3]. This is dangerous because when the leaflets in the valve don’t meet correctly, blood may leak backwards into the lungs each time the heart pumps. If blood leaks backwards, the heart has to pump harder in order to push the same amount of blood forward. This is known as volume overload. The heart may compensate for this overload for many months or even years but eventually the heart begins to fail and patients show symptoms of shortness of breath or fatigue[3].
Causes
Mitral valve problems are mainly due to simple wear and tear that causes part of the valve mechanism to fail. Rheumatic fever may also damage the mitral valve causing stenosis or regurgitation, and occasionally the mitral valve is damaged by infection or bacterial endocarditis. Coronary artery disease may also cause the mitral valve to leak[3].
Symptoms
Some symptoms experienced by patients who need mitral valve repair or replacement include: unusual sensations of feeling the heart beat; chest pain; difficulty breathing (especially after activity); fatigue; coughing; and shortness of breath while lying flat. These symptoms may develop slowly, or the patient may not have any symptoms at all.[4]
Options
Some surgeons will first recommend repairing the valve instead of replacement, but if the patient is not a good candidate then they must replace the valve.[5]
Many mitral valves can be repaired, especially if the leak is due to wear and tear. When the valve is too damaged to repair, the valve must be replaced with an artificial valve[6]. There are some advantages to repairing a mitral valve versus replacing it. Some of these advantages are; a lower mortality at the time of operation (1-2% for repair versus 6-8% for replacement), a significantly lower risk of stroke, and a lower rate of infection, improved long-term survival with mitral valve repair. Patients who receive a valve repair stay on the same survival curve as the normal population. A survival curve tends to be a graph of downward steps with the x-axis as time in months and the y-axis as percent still alive.[7] After mitral valve repair, blood thinners are not required, in contrast to the life-long requirement for blood thinners after mechanical mitral valve replacement[8].
Non-Surgical Options
Most patients can endure surgery without complications; however, there are some whose heart functions are too weak to withstand surgery. Non-surgical approaches to treat heart valve disease without surgery are divided into three categories: Clinical Practice treatment (this is used in every day clinical practice), Investigational treatment (current clinical studies that are underway), Early Development treatment (early stages of investigation).[9]
Types of Valves
There are two primary types of artificial mitral valves -- a metal or mechanical valve and a tissue valve or biological valve.[10] The mechanical valves are made entirely from metal and pyrolytic carbon and last a lifetime[6]. With this valve, patients are required to take blood-thinning medications to prevent clotting. The tissue valve is made from animal tissues[6]. The tissue valve doesn’t require a patient to take blood thinners, but it only last 10 to 15 years.[10] The choice of which type to use should be made by you and your doctors taking the following into consideration: your age, medical condition, preferences with medication, lifestyle[11].
Details of the procedure
A mitral valve replacement procedure is performed under general anesthesia, which will keep the patient asleep during the whole surgery.[2] The preferred method is to first make an incision under the left breast rather than through the breastbone in the front of the chest, to get to the heart. After the heart is exposed, blood must be rerouted to a heart-lung machine (cardiopulmonary bypass)[12]. An incision is made in the left atrium to expose the mitral valve. The valve is then replaced with either a biological valve or mechanical valve. The heart is then closed with sutures[12]. The patient is then taken off the cardiopulmonary bypass and blood is allowed to flow into the coronary arteries. If the heart does not beat on its own, an electric shock is used to start it. Then the chest is closed up[12].
Risks
With mitral valve replacement surgery, there are risks such as bleeding, infection, or a complicated reaction to anesthesia[13]. Each risk is determined best with each patients own cardiologist and cardiothoracic surgeon. They will better know each individuals medical history and conditions. Risks depend on a patient’s age, general condition, specific medical conditions, and heart function[11].
Postoperative Complications/ Risks
A common postoperative complication with mitral valve surgery in a study involving 99 patients who had surgery for mitral regurgitation from January 1990 to June 1996 is atrial fibrillation. This occurred in 32% of patients. A common pulmonary complication is congestion necessitating prolonged use of oxygen. Other patients required prolonged ventilation of longer than 24 hours for conditions like pulmonary edema, ARDS, and pulmonary thromboemboli[14]. Nine patients had renal failure with six of them dying within 30 days after their operation. Five patients had permanent strokes, and nine patients were readmitted to the hospital within 30 days of their discharge[14].
Effectiveness
In a clinical study done of 99 patients who had mitral valve surgery for regurgitation from January 1990 to June 1996, long-term and short-term outcomes were evaluated. These evaluations included; mortality rate, clinical complications, readmissions, valve deterioration, reoperation, and health perception. Overall mortality was 4%, which included 3 operative deaths and 4 late deaths. Overall 5-year survival rate was 92%[14].
Condition after mitral valve replacement
After the surgery the patient is taken to a post-operative intensive care unit for monitoring. A respirator may be required for the first few hours or days after surgery. After a day, the patient should be able to sit up in bed. After two days, the patient may be taken out of the intensive care unit. Patients are usually discharged after about seven to ten days[12]. If the mitral valve replacement is successful, patients can expect to return to their regular condition or even better. Patients who have biological valve are prescribed blood thinners (Anticoagulation) with Coumadin for 6 weeks to 3 months postoperative, while patients with mechanical valves are prescribed blood thinners for the rest of their lives. These blood thinners are taken to prevent blood clots that can move to other parts of your body and cause serious medical problems, such as a heart attack. Blood thinners will not dissolve a blood clot but they prevent other clots from forming or prevent clots from becoming larger. [15] Once the patient’s wounds are healed they should have few, if any, restrictions from daily activities[16]. Patients are advised to walk or undertake other physical activities gradually to regain strength. Patients who have physically demanding jobs will have to wait a little longer than those who don’t. Patients are also restricted from driving a car for six weeks after the surgery[17]. Once a person has a mitral valve procedure, they are required to have prophylactic antibiotics as a preventative measure against infection whenever they have dental work done[18].
Depending on the method of surgery, some scarring will occur. If the breastbone is divided, the patient will have a long scar along the breast bone. If the heart is accessed from under the left breast there will be a smaller scar in the spot.
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