Mitral valve replacement
|Mitral valve replacement|
Starr-Edwards mitral valve
Mitral valve replacement is a cardiac surgical procedure in which a patient’s diseased mitral valve is replaced by either a mechanical or bioprosthetic valve. Mitral valve replacement is performed 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 back into the left atrium and thereby back into the lung. Mitral valve disease can occur from infection, calcification, inherited collagen disease, or other causes. Since a mitral valve replacement is an open heart surgical procedure, it requires placing the patient on cardiopulmonary bypass.
- 1 Normal anatomy and physiology
- 2 Mitral stenosis and regurgitation
- 3 Effectiveness
- 4 Risks
- 5 Artificial valve types
- 6 Procedure
- 7 Recovery
- 8 Alternatives
- 9 See also
- 10 References
- 11 Sources
- 12 External links
Normal anatomy and physiology
Mitral valve is a bi-leaflet valve sited between the left atrium and left ventricle, responsible for the prevention of blood flow from the atrium to the ventricle during contraction. Its shapes is elliptical and its area varies from 5,0 to 11,4cm2. Leaflets are separated by two commissures, and each leaflet of the valve (anterior leaflet, the large one, and posterior leaflet, the small one) is separated in 3 sections (p1, p2, p3)Histologically, each leaflet has is composed by the solid fibrosa, the spongiosa at the atrial surface and another fibroelastic layer covering the leaflets.  Two pappilary muscles that originate from the base of the left ventricle are holding mitral leaflets in place through Chordae Tendinae which insert the edge of the leaflets, preventing them from leaking during left ventricle systole.
Mitral stenosis and regurgitation
The most common cause of mitral stenosis is rheumatic fever, by far, which is seen mostly in the third world. Other causes are mitral degenerative disease, severe calcification (elderly), congenital deformities, malignant carcinoid syndrome, neoplasm, LA thrombus, endocarditic vegetations, certain inherited metabolic diseases, or complications of previous procedures at the aortic valve. Because of the stenosis, left atrium pressure increases, which, if left untreated might lead to dilatation, hypertrophy, atrial fibrillation and thrombus creation. Symptoms include dyspnea on exertion, orthopnea or paroxysmal nocturnal dyspnea and fatigue.
Failure of mitral leaflets to coapt effectively results in regurgitation of blood from left ventricle towards left atrium during systole. Most common causes are myxomatous degeneration (Barlow disease), ischemic heart disease, dilated cardiomyopathy, rheumatic valve disease, mitral annular calcification, infective endocarditis, congenital anomalies, endocardial fibrosis, myocarditis, and collagen-vascular disorders. The most used system of classification of mitral valve regurgitation is Carpentier's classification, which uses pathologoanatomich features to separate mitral regurgitation to three types. at Type I, the leaflets are moving normally, at type II leaflet motion is excessive and at type III their movement is restricted.
In a study of 99 patients who had mitral valve surgery for regurgitation from January 1990 to June 1996, overall mortality was 4%, which included 3 operative deaths and 4 late deaths. Overall 5-year survival rate was 92%.
With mitral valve replacement surgery, there are risks such as bleeding, infection or reaction to anesthesia. Risks depend on a patient’s age, general condition, specific medical conditions, and heart function. Neuropsychological and psychopathologic changes following mitral valve replacement surgery have been recognized from the very beginning of modern heart surgery.
Variables correlated with nonpsychotic mental disorder after cardiac surgery must be divided into pre-, intra- and postoperative. The incidence, phenomenology, and duration of symptoms diverge from patient to patient, and are difficult to define. One wonders whether any of the patients in either group in this analysis underwent any mechanical cardiac valve replacement. If so, one has to consider Skumin syndrome, described by Victor Skumin in 1978 as a “cardioprosthetic psychopathological syndrome” associated with mechanical heart valve implant and manifested by irrational fear, anxiety, depression and sleep disorder.
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  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.
Artificial valve types
There are two primary types of artificial mitral valves: mechanical valves and bioprosthetic tissue (biological) valves. The mechanical valves are made from metal and pyrolytic carbon, and can last a lifetime. Patients with mechanical valves must take blood-thinning medications to prevent clotting. Bioprosthetic valves are made from animal tissues. Use of these biological valves allows patients to avoid blood thinners. However, the bioprosthetic valves may only last 10 to 15 years. The choice of which valve type to use depends upon the patient's age, medical condition, preferences with medication, and lifestyle.
People having mitral valve surgery receive general anesthesia. Incision can be made somewhat horizontally under the left breast, or vertically through the sternum. After the heart is exposed, canulae are placed to reroute blood to a heart-lung machine for cardiopulmonary bypass. An incision is made in the left atrium to expose the mitral valve. The valve is then replaced with either a biological or mechanical valve. The left artium is then closed, and the patient weaned from cardiopulmonary bypass. After surgery patients are typically taken to an intensive care unit (ICU).
Mitral valve surgery can now also be performed robotically although the procedure may take longer.
New Developments (2014 -2017): Transcatheter mitral valve replacement or TMVR involves human heart mitral valve replacement without recourse to open-heart surgery. TMVR treats mitral valve stenosis and/or mitral valve regurgitation leading to mitral insufficiency. TMVR, initially developed by the company Tendyne (a subsidiary of Jean Boulle Medtech Ltd) for open-heart high risk patients is expected to replace traditional mitral valve replacement surgery in the longer term. The Tendyne mitral valve is placed inside a beating heart via a transcatheter at the bottom of the heart through a tube inserted in a small incision in the patient’s chest. The physician uses the tube to deploy the valve and positions it so that it rests over the heart's existing mitral valve. It is then anchored securely in place by an adjustable tether. The valve is fully retrievable, totally repositionable and is sewn onto a Nitinol frame. Nitinol is a superelastic nickel and titanium "shape memory alloy" whose flexibility eases implantation, but regains its original shape when it returns to a patient’s normal body temperature.
The transition of TMVR from concept to reality occurred during the period 2014 -2017.
After the surgery the person 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. 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 (anticoagulants) with warfarin 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 the 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.
Once the person’s wounds are healed they should have few, if any, restrictions from daily activities. People 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.
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. Some scarring occurs after surgery. For median sternotomy (access through the sternum, or breastbone), the patient will have a vertical scar on the anterior chest above the sternum. If the heart is accessed from under the left breast there will be a smaller scar in this location.
Many mitral valves can be repaired instead of replaced, especially for minimally damaged valves. Advantages to valve repair instead of replacement include lower surgical mortality (1-2% for repair versus 6-8% for replacement), lower risk of stroke, lower rate of endocardial infection, and improved long-term survival.
Patients who receive a valve repair stay on the same survival curve as the normal population. After mitral valve repair, blood thinners are not required; however, lifelong maintenance on blood thinners is required after mechanical mitral valve replacement.
For individuals with few symptoms, or those with contraindications to surgery, there are options for medical treatment in both mitral insufficiency and mitral valve stenosis, although they are non-curative. For both conditions, such medical treatments may include diuretics, vasodilators, and ACE inhibitors.
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