Mitral and Aortic Valve Repair and Replacement
The heart has four valves. These are:
- Mitral valve. This valve is located between the upper left chamber (left atrium) and the lower left chamber (left ventricle). It has two flaps or leaflets and a complex supporting apparatus attached to the internal wall of the left ventricle
- Aortic valve. This valve is located between the lower left chamber (left ventricle) and the aorta, which is the big blood vessel through which red (oxygenated) blood from the left heart passes to the body. It has three flaps or leaflets
- Tricuspid valve (also called the right atrioventricular valve). This is located between the right upper chamber (right atrium) and right lower chamber (right ventricle). It has three flaps/leaflets
- Pulmonary valve. This valve is located between the right lower chamber (right ventricle)and the pulmonary artery. It has three flaps/leaflets and controls blood flow into the lungs through the pulmonary artery
For efficient heart function, the valves must be able to open fully while the blood is passing through, then close tightly afterwards. Simply put, blood should flow only in one direction.
Abnormal or diseased valves allow less blood to pass through and/or allow blood to leak backwards. This may be due to:
- Weakened leaflets
- Fusion of the leaflets
- Holes or tears in the leaflets
- Deformity of the valve leaflets due to scar tissue
- Hardening of the valve leaflets due to calcium
To resume efficient function, diseased valves need to undergo a surgical procedure to either repair the valve or replace the valve.
This is the preferred treatment if suitable because you retain your native valve and avoid blood thinners or other long term concerns associated with valve replacement. The faulty valve is repaired by:
- Cutting through and separating fused leaflets
- Patching holes and sewing tears on leaflets
- Reshaping deformed valves by removing excess tissue, scars and calcium deposits
This is done only when repair is not possible. The diseased valve is removed and replaced with either a man-made metallic valve or a biological valve (from pig, cow or human tissue).
Metal valve vs. biological (or bioprosthetic) valve
- Metal valves last a long time and are designed to last longer than a human lifespan.
- Bioprosthetic valves eventually wear out as the human body identifies that they are not normal tissue. This takes 10-18 years for aortic, pulmonary and tricuspid valve bioprostheses and 7-10 years for mitral bioprostheses
- Persons with metal valves are maintained on lifelong warfarin (a blood-thinning medicine) to prevent clots forming on the valve that would cause a stroke or obstruction to valve opening. Warfarin carries a lifelong risk of bleeding particularly if the blood levels are not tightly controlled
- Bioprosthetic valves do not require blood thinning medication after they have healed in the heart 3 months following the operation
- Metal valves are recommended for younger individuals in order to avoid further operations
- Bioprosthetic valves are recommended for the elderly, for women of childbearing age and when people want to have a normal lifestyle but accept the need for a repeat operation to replace a deteriorated valve in the future
Conditions that may require mitral valve repair or replacement
When the heart beats and blood in the left lower chamber, which is supposed to be pumped out towards the other parts of the body, leaks back to the left upper chamber, a condition called mitral regurgitation exists. It could be due to weak valve flaps (the mitral valve has two). Sometimes the flaps even protrude backwards, a condition known as mitral prolapse.
Mitral stenosis is a condition when the mitral valve does not fully open thereby allowing only a small amount of blood to pass through from the left auricle to the left ventricle. It could be that the flaps of the valve got stuck to each other (fused), or they may have stiffened or hardened due to scars, calcified deposits or plaques.
Conditions that may require aortic valve repair or replacement
Aortic insufficiency (also known as aortic regurgitation)
The aortic valve is unable to snugly close, allowing blood that has already flowed out to the aorta to flow back to the left ventricle of the heart. This might be due to softening or weakening, tear, or a disfigurement of the flaps.
The aortic valve is unable to open fully, thereby allowing only a small amount of blood to pass through towards the aorta. This might be due to scarring, adhesion or sticking together (fusion) of the flaps of the valve, or the presence of waxy deposits or plaques in the valves.
How the valvular heart surgery procedure is done?
The procedure is performed in the operating room by a heart surgeon under general anaesthesia with assistance of the heart-lung machine. Tubes for delivery of oxygen and IV fluids are hooked up and the sternum is opened in the midline to expose the heart. The patient is put on the heart-lung bypass machine (also called cardiopulmonary bypass pump) to ensure continuous oxygenated blood flow to all parts of the body except the heart and the heart (coronary) arteries.
Meanwhile, the heart is stopped beating by lowering its temperature and using blood containing a high potassium solution to cause it to stop temporarily. Repair or replacement of the diseased valve(s) is then performed utilizing any of the specific procedures listed under valve repair and valve replacement above.
The heart then resumes beating by restoration of blood flow through the heart arteries at the completion of the valvular surgery.
When the heart is seen to be beating normally again, the heart-lung bypass pump is withdrawn and excess blood around the operation area is suctioned off and chest drainage tubes are placed. Temporary pacing wires are also sometimes attached to the heart and brought out through the chest wall to control the heart rhythm after the operation.
The chest incision is then closed and dressed, and the surgery is completed. The sternum bone is put back together using stainless steel wires that remain in place as the bone heals. They are inert, do not set off metal detectors and are MRI compatible after 6-8 weeks. The remainder of the wound is closed using absorbable (dissolving) sutures.
After heart surgery, the patient is allowed to recover for a few days in the intensive care unit where vital signs are closely monitored. Once awoken and weaned from the ventilator they are moved to the step down unit and then to the post-operative ward. Most often, pain medication, antibiotics and anti-coagulants are given. Mobility is increased each day with the assistance of the physiotherapist and the patient must work on deep breathing and coughing exercises to clear and expand the lungs in order to prevent pneumonia. When the range and duration of movement and physical activity have increased (usually in 5-7 days), the patient is allowed to go home.
Recuperating at home, the patient needs to consider certain things, such as:
- Medications. You may need to continue certain medications for a lifetime (such as the anti-clotting medicine warfarin)
- Wound care
- Exercise and physiotherapy
- Complications to watch out for
- When to go back to work
- Check ups
- Lifestyle modifications
- Cardiac rehabilitation. Cardiac rehabilitation is a clinically supervised program to help heart patients recover and regain their overall physical and mental functioning. This helps to prevent recurrent heart attacks.Cardiac rehabilitation programs include education about cardiac health, lifestyle modifications, psychological support, nutritional advice and much more.
It is best to have a detailed talk with Dr Orr regarding these before going home. So, make sure that all necessary contact numbers are listed down.
Nowadays, the success rate of open heart surgeries, valve repair and replacement included, is very favourable. More so if the disorder or defect is corrected at a stage before severe irreversible complications have set in. Other determining factors for the success of valve repair and replacement are age (the younger the better), previous lifestyle (those who don’t smoke, drink, and have healthy diets tend to fare well), and, of course, the new lifestyle the patient chooses.