Mitral Valve Surgery
Background
The Mitral valve is one of the four valves in the heart. The mitral valve is composed of two leaflets that open and close with the rhythm of the heart. The valve leaflets open and close in a very similar fashion to “French or double doors”—opening widely when both leaflets are pushed open by the blood flow from the left atrium into the left ventricle and closing to meet in as the left ventricle contracts or beats and the edges of the valve leaflets come in contact to seal the valve closed.
Location
The Mitral valve is located in the left side of the heart in the chamber of heart known as the left atrium. The mitral valve is the opening between the Left Atrium and the Left Ventricle. All the valves in the heart are “one way valves” that is, the blood flowing through the valves is supposed to flow in only one direction.
Physiology or Function of the Mitral Valve
After the blood receives oxygen from the lungs, it flows into the left atrium. The mitral valve is the valve that keeps the blood in the left atrium until the left ventricle is ready to accept it. The blood flows across or through the mitral valve into the left ventricle. As the left ventricle contracts, the mitral valve closes keeping the blood in the left ventricle so it can be pumped out of the left ventricle through the aortic valve and to the rest of the body. The left ventricle is the part of the heart that generates the blood pressure your doctor or nurse measures when you visit their office.
Mitral Valve Diseases or Conditions
There are two major conditions that affect the Mitral Valve,
- Mitral Stenosis, which is a narrowing of the valve, which inhibits or blocks the free flow of blood through the valve
- Mitral Regurgitation or Insufficiency, in which the valve is “leaking” and allowing blood to move forward and backward through the mitral valve.
Mitral Valve Stenosis: In this condition the mitral valve becomes scarred because of inflammation or becomes calcified. In the United States, the main cause of mitral stenosis used to be an episode of rheumatic fever as a young child or young adult. However because rheumatic fever has been for the most part eliminated in the USA, the incidence or occurrence of mitral stenosis is relatively low.
In Mitral stenosis the two leaflets of the mitral valve become stiff, or become stuck together or become calcified and cannot open freely or fully. The opening of the valve therefore becomes narrowed and blood flow through the valve is impeded or increasingly “blocked”.
Mitral Valve Insufficiency or Regurgitation: The other mitral valve condition is known as Mitral valve insufficiency or mitral valve regurgitation. In this condition the mitral valve leaflets do not come together and the blood flow can go forward and backward across the valve. If we think of the valve leaflets as “French doors” the leaflets can either not meet in the middle because one “door” or leaflet” opens too much in the wrong direction, leaving an opening between the two doors, which in medical terms is known as “mitral valve prolapse”. The other main condition that causes mitral valve insufficiency is when the supporting structure of the two leaflets, (known as the mitral valve annulus) becomes stretched and the two leaflets are pulled apart and cannot meet in the middle. Again using the “French door” example, the doorframe becomes damaged and too big for the doors, so the doors cannot meet in the middle.
Other conditions that can cause mitral insufficiency are a) a heart attack that damages the supporting muscles of the mitral valve leaflets or (b) an infection of the mitral valve, which destroys the integrity of the valve leaflet.
Symptoms of Mitral Valve Disease
The main symptoms of both mitral valve stenosis and mitral valve insufficiency are usually:
- Shortness of breathe with exertion
- A feeling of being tired
- Rapid Heart Rate (palpitations)
- Difficulty lying flat when trying to sleep
- Swelling of the ankles
- In severe cases Shortness of breath at rest.
These symptoms are often lumped together as “congestive heart failure”. The symptoms occur because the blood flow through the left atrium is either impeded or blocked when the valve is too tight or “stenosed” which causes the blood to back up into the lungs and the lungs become “congested”. In Mitral valve insufficiency, the blood flows backwards through the mitral valve as the left ventricle contracts and again the lungs become too full of blood or “congested” which in turn causes the shortness of breath.
With both mitral valve stenosis and mitral valve insufficiency, many people can do well as long as the condition is mild or moderated, don’t try to exercise to hard and take the appropriated medications. It is only when the stenosis (narrowing) or leakage (‘insufficiency/regurgitation) become moderated-severe and the patient becomes increasingly short of breath and is hospitalized for reaped episodes of congested heart failure is surgery indicated. The leakage or insufficiency of mitral valve insufficiency is grated 1 –to 4 Plus with 1+ being mild- 2+ being moderate, 3+ moderated to severe and 4 + being severe. In most cases surgery is not indicated unless the valve leakage is grated 2-4 +
Surgery for Mitral Valve Diseases
Indications for surgery:
As noted, many patients can live most or all of their lives with mild mitral valve stenosis or insufficiency. For instance, a condition known as mitral valve prolapse, which causes mitral valve insufficiency (leakage) is relatively common in women, however, many women live all their lives without ever needing surgery for their mitral valve prolapse.
The indications for surgery are based upon the symptoms the patient is having and some anatomical findings that the work up for the mitral valve problem will show.
For mitral valve stenosis, once the valve becomes narrowed enough to begin causing the patient symptoms of congestive heart failure (shortness of breath with exertion or exercise, swelling in the legs, difficulty exercising, an inability to lay flat) surgery is usually indicated.
For mitral valve insufficiency, the leakage is graded from 0 to 4+, with 0 being no leak and 4+ the leakage being wide open. Usually with a leakage score of less than 2+ the patient can be managed medically and surgery is not indicated unless the symptoms are more than the patient wants or can deal with. Once the leakage score becomes greater than 2 + then surgery is usually indicated to prevent long-term heart damage that occurs from the heart compensating for the damaged mitral valve.
The Surgery/Procedures for Mitral Valve Stenosis and Mitral Valve Insufficiency:
There are two basic procedures for any mitral valve problem:
- Mitral Valve Replacement
- Mitral Valve Repair
In most cases the surgeon will try to repair the damaged valve, if a good, long lasting repair can be accomplished. However, like with any damaged item, sometimes a repair can be performed and sometimes the damage is too extensive and the item or part must be replaced.
Mitral Valve Replacement
In a mitral valve replacement operation, the surgeon removes all or most of the damaged valve and sews in a man made valve to replace the patient’s damaged mitral valve.
There are two kinds of man-made valves available to replace a damaged mitral valve.
- A tissue valve that is made from a pig valve (porcine) or cow tissue (bovine).
- A metal or “mechanical” valve that is made of high tech metal
Both the tissue and mechanical mitral valves are sewn in the same way, but both have advantages and disadvantages.
The mechanical mitral valve have the advantage that it will for the most part never “wear out” and should last the patient the rest of their life. The disadvantage is that the mechanical valves require that the patient be anti-coagulated for the rest of their life, usually with a drug known as Coumadin or Warfarin. Many people refer to the “anti-coagulation” as “thinning the blood” but in actuality the blood is not “thinned”. The Coumadin acts to keep the blood from clotting as easily as it normally would. The effect of the Coumadin on the patient’s anti-coagulation must be closely managed. If the blood becomes too anti-coagulated the patient will have bleeding problems, which can be severe. If the blood is not anti-coagulated enough, the mechanical mitral valve will form clot that can stick the valve open or closed, both of which can be life threatening problems, or the clot can become dislodged and cause a stroke or move down stream in the blood vessels and block off an artery some where else in the body.
Generally, mechanical valves are recommended to younger patients, i.e. younger than 60 or 65 and sometimes to patients on renal dialysis (because dialysis patients wear out a tissue valve quickly). A woman who wants to have more children should not have a mechanical valve because of the need for Coumadin.
The tissue mitral valves have the advantage that they do not require life long anti-coagulation. Some surgeons will place the patient on Coumadin for a month after the surgery, but in most cases the Coumadin can be stopped after a month. The disadvantage of the tissue valves is that they do eventually wear out. They generally do not suddenly wear out, but when they do, the only way to deal with the problem is to repeat the operation, remove the worn out valve and replace it with another tissue valve.
Tissue valves are usually recommended for older patients, i.e., 65 and older. The statistical facts are that in older patients the tissue valves that are currently available will last 15-20 years and that in most instances the valve will out last the patient. Additionally, the risks of taking Coumadin and the consequences of bleeding complications increase for patients over 65.
Mitral Valve Repair
Mitral valve repair is what most surgeons will try to perform, if the damaged mitral valve looks repairable with the pre-operative studies and what the surgeon finds at surgery. There are numerous techniques that a surgeon can use to repair a damaged valve, which depends on the type of damage the surgeon finds at surgery
The mitral valve repair usually is supported with an artificial strip or “band” of man made material or in some instances the surgeon may place a man made ring around the valve to support the valve repair or help reshape the mitral valve structure.
The advantage of a mitral valve repair is that the patient does not have to take life long Coumadin. The disadvantage of any repair is that the repaired valve can over time again become damaged--- just like anything we “repair” in life the item can over time become “worn out” again. If or when the repaired mitral valve again wears out, the options at that time are to repeat the operation and usually at that time replace the valve with either a mechanical or tissue valve.
The Surgical Approaches to Mitral Valve Replacement or Repair
The usual or standard approach to almost all heart surgeries are via an incision known as a “median sternotomy”, which is an incision down the middle of the patients breastbone or sternum. This approach gives the surgeon full access to all of the heart structures and is needed to perform most heart surgeries, especially if the patient requires a combination of heart operations at once, such as a mitral valve operation plus another valve or a coronary artery bypass operation.
The other surgical approach to mitral valve surgery is via an alternative smaller incision. This approach is often referred to as “minimally invasive” since the incision is smaller. The approaches to a “minimally invasive mitral valve procedure” include:
- A “mini-sternotomy” in which only the lower half of the sternum or breastbone is divided
- A small incision between the ribs on the right chest, usually about the level of the nipples on a man and in the crease underneath a woman’s breast.
- Robotic assisted mitral valve surgery. In this procedure a da Vinci robot is used to do the surgery. The robot arms are guided by the surgeon through several small incisions (1/2 inch or less) on the patient’s right rib cage.
In all of the minimally invasive procedures there is also a small incision in the right or left groin to access the artery and vein in the groin (femoral artery and femoral vein), which are used as access for putting the patient on the heart lung machine to perform the surgery.
The advantages for a “minimally invasive approach is that the incisions are smaller and in most instances less painful than a full median sternotomy. Although in some cases the incisions between the ribs can be much more painful than an incision through the breastbone. Additionally any minimally invasive approach does require multiple incisions and an incision in the groin. The other potential advantage for minimally invasive surgery is that the right chest or right rib cage and the lower ½ sternotomy incisions are not visible with the usual shirt or blouse worn post operatively.
The disadvantages of a minimally invasive approach is that the procedure does take longer than the operation done through a median sternotomy and if there is a problem during the minimally invasive approach the surgeon may have to abandon that approach and use a median sternotomy to fix a problem.
Your surgeon will talk with you regarding the best way to perform your surgery. Not everyone one is a candidate for a “minimally invasive” operation.
Some potential contraindications to a minimally invasive approach include:
- Diseased femoral arteries that is too small or calcified to use for the heart –lung machine
- Morbid Obesity
- Severe COPD (bad lung disease)
- Prior open-heart surgery
- The need for multiple cardiac procedures such as multiple valve operations or mitral valve plus bypasses for blocked heart arteries, known as coronary artery disease.
Mortality and Morbidity (Death and/or Complications)
Any open-heart surgery is considered a major operation. However, despite the fact that open-heart surgery is a major procedure, in most cases the risk of death is very low. The average risk of death (mortality) is between 3-5%. The likelihood of death in the operating room is almost zero with the medicines and other life saving equipment available.
The likelihood of complications is also very small, again around 3-5 % for most patients. The list of potential complications is long and there are many “what if’s” however, the most common complications for mitral valve surgery are:
- Post operative bleeding, which some times may require a return to the operating room to fix the problem.
- The potential need for a blood or blood product transfusion
- Stroke
- Heart damage or a heart attack
- Potential need for a permanent pacemaker
- Infection of the incisions or in very rare instances an infection of the artificial valve.
- Other complications such as kidney trouble, pneumonia are also rare.
Hospital Stay
In most instances mitral valve surgery usually requires at least 24-48 hours in an intensive care unit. Once the patient is stable enough or strong enough to leave the intensive care unit, they are transferred to a cardiac surgery step-down unit and stay in the hospital generally another 5-7 days before they are ready for discharge. In most instances the post op recovery time at home is 6 to 10 weeks depending on the pre-operative condition of the patient, age and motivation to resume a normal life.
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