The healthy mitral valve closes when the heart contracts and opens to allow blood to flow into the heart when the heart relaxes.
A degenerative mitral valve with a flail (detached) leaflet will not close properly and therefore allows blood to leak backwards into the lungs.
The heart is a complex pump with 4 one-way valves. The mitral valve is located between the left atrium and the left ventricle. Valves cease to function appropriately when the valve fails to open properly limiting the blood flow (mitral stenosis) or when the valve fails to close causing a large backwards leak (mitral regurgitation). Mitral regurgitation (MR) or a leaking mitral valve is most commonly caused by mitral valve prolapse where a section of the valve does not close properly. This is the most common cause of mitral valve disease in Australia.
The Mitral Valve
The mitral valve is made of two leaflets than usually open and close freely. They are similar to a double-door and are prevented from opening in the opposite direction by chords that are attached to the edges of the leaflets (the doors). The leaflets are hinged on the annulus which is akin to the doorframe.
There are a number of causes for a mitral valve to leak:
-The annulus can be dilated so that the ‘doorframe’ is too wide for the doors (leaflets) causing a leak at the centre of the valve
-The chords can rupture so that the leaflet swings back too far
-A leaflet can have a hole in it (usually from infection)
Regardless of the cause, if a patient has severe mitral regurgitation and especially if they have symptoms, surgery should be considered.
With significant mitral regurgitation some of the blood is being pushed back towards the lungs instead of flowing out of the heart into the body. This results in a number of deleterious effects including significant shortness of breath, enlargement of the heart, palpitations, and ultimately heart failure.
Mitral regurgitation can be corrected with either a valve replacement or valve repair. An excellent mitral valve repair is a superior option to replacement with better survival and decreased chance of infection.
Mitral valve disease may be picked up incidentally with a routine check up when a doctor can hear a ‘murmur’ in the heart with their stethoscope. This can often be discovered during childhood checks and many patients are aware that they have had mitral valve disease many years before they require surgery.
In other situations patients may present to their general practitioner with shortness of breath on exertion and a new heart murmur is discovered. They will be referred to a cardiologist who will perform an ultrasound of the heart – an echocardiogram. This will provide a detailed look of the interior of the heart – its function and the degree of mitral regurgitation or stenosis.
If someone has severe mitral regurgitation or stenosis they may be referred to a cardiothoracic surgeon for consideration of valve repair or replacement.
The faulty mitral valve is replaced with a new valve. This is an example of a bioprosthetic or tissue valve which is constructed from the lining of a cow heart (bovine pericardium).
Who needs this procedure?
If someone has severe mitral regurgitation or mitral stenosis they may require surgery to repair or replace the mitral valve. Symptoms that can be noticed with mitral valve disease include shortness of breath, particularly on exertion or when walking up a hill or stairs. Other common symptoms are heart palpitations when the heart feels like it is ‘racing’ or beating irregularly.
Mitral valve disease can ultimately result in heart failure and this can present shortness of breath at rest, the inability to lie flat, waking up in the middle of the night short of breath and leg swelling.
Patients who have severe mitral regurgitation and have symptoms should undergo assessment by a cardiothoracic surgeon for consideration of mitral valve repair or replacement. Patients who don’t have symptoms are monitored regularly by their cardiologist. If the heart starts to fail or enlarge even without symptoms, surgery should be considered.
What is involved?
Open mitral valve surgery is performed under general anaesthetic through a vertical incision down the middle of the breastbone (sternum) to expose the heart. The patient is connected to a heart-lung machine, which pumps blood through the body whilst the heart is stopped to operate on it. The mitral valve is accessed and repaired or replaced according to its condition. The operation takes approximately 3-4 hours.
Mitral Valve Repair
In most cases of mitral regurgitation, the valve can be repaired by using a number of complex techniques to reconstruct its function. Mitral valve repair has been associated with improved long-term survival because the heart function is preserved with the more natural function of a repaired native valve. There is also a reduced chance of infection compared with replacement as there is far less foreign material for bacteria to grow on. Another significant consideration is that for younger patients, valve repair means that they can live without the blood thinner warfarin which would have been required for a mechanical (metal) valve replacement.
Mitral Valve Replacement
Mitral valve replacement is indicated for patients with mitral stenosis and in some cases for mitral regurgitation. The faulty valve is replaced with an artificial valve from these two broad categories: tissue valves and mechanical valves.
Generally, patients under the age of 60 will choose a mechanical valve and patients older than 65 will choose a tissue valve due to the differences in longevity of the valves and the need to be on blood thinners. In younger patients, tissue valves are found to be less durable for reasons that aren’t completely clear but may relate to their stronger immune system. When the valve fails a repeat surgery is generally required to place a new valve.
A mechanical valve will essentially last forever mechanically but requires the blood thinner warfarin for life. This is because the natural blood clotting system ‘sees’ the mechanical valve as foreign and will form a clot. If there is clot formation on a valve it can cause a catastrophic failure. Warfarin is a strong blood thinner that requires regular blood testing to monitor its effect and increases the risk of bleeding with trauma and surgery.
Ultimately, the choice of valve is individual and Dr Bassin will discuss this with each patient in detail.
- Is made from cow or pig material
- Is more usually suitable for patients over 65
- Will usually last for 10 years before needing a replacement
- No long-term requirements to take blood thinners
- Is sometimes referred to as a metal valve, but is actually constructed from pyrolytic carbon
- Is more usually suitable for patients under 60
- Will last mechanically forever
- Requires the patient to take the blood thinner ‘warfarin’
What is the recovery like?
The operation takes approximately 3-4 hours and you will wake up in intensive care later that day or the next morning. Small tubes to drain any residual fluid from around the heart will be placed in your neck, as well as intravenous lines, to sample blood and administer medications. These tubes and lines will be removed after 1-2 days and then you will be transferred to the ward to continue your recovery.
Once on the ward, the goal is to monitor your blood pressure and heart rate and ensure adequate mobilisation. We work very closely with our nurses, physiotherapists and occupational therapists to work on breathing exercises and functional mobilisation. Every patient is different and the assistance is tailored to your needs. Many patients are discharged home after a week but there is a significant number of patients, particularly the elderly who find it easier to transition home after a short stay in a rehabilitation hospital.
Once at home, patients are encouraged to take plenty of walks and to generally take it easy. Your body will let you know what it is capable of and there is no need to push it during this recovery period.
For the first 6 weeks there are precautions to be taken whilst the bone is healing. Lifting should be limited to 3kg and patients are encouraged to sleep on their back. Any activity that requires heavy use of the arms is generally discouraged.
Patients generally go back to work after 4-6 weeks and complete recovery is achieved by 3 months.
A successful mitral valve repair provides better long-term survival.
What are the benefits and risks of this procedure?
Mitral valve replacement has been performed since the 1960s with excellent results. We have continued to improve the safety of surgery but there are still risks. For patients who are otherwise well the risks of surgery include: death (1%), stroke (1%), significant wound infection (1%), kidney injury (2%), requirement for a permanent pacemaker (3%) and blood transfusion (25%). The risk can be higher if patients have other co-morbidities including advanced age, previous heart disease or stroke, lung disease or having undergone cardiac surgery previously.
Dr Bassin will explain these risks to you in person as they pertain to your condition.
When can I drive?
You may drive 4 weeks following surgery, according to the national guidelines.