Heart valves: operations and procedures
Heart valve operations are carried out to repair or replace damaged or malformed heart valves. There are various techniques available. Replacement surgery involves the transplantation of either artificial heart valves or heart valves made from animal tissue.
Heart valves ensure that blood flows in the right direction when it is pumped by the heart. In total, there are four valves that perform this function: the aortic valve, the pulmonary valve, the mitral valve and the tricuspid valve.
The most common cause of heart valve damage is calcification, which is similar to arteriosclerosis. Other possible causes include inflammation of the valves caused by bacteria, viruses or rheumatism. In rare cases, people are born with valve defects.
If the heart valves can no longer open due to damage, this is known as heart valve stenosis. If they no longer close completely, this is called heart valve insufficiency. Both conditions place additional strain on the heart and over time can damage the heart if left untreated.
Damaged heart valves must be treated surgically. If a valve cannot be reconstructed, it is replaced using either an artificial, mechanical heart valve or a biological heart valve made from animal tissue.
Heart valve reconstruction
Whether or not a heart valve can be reconstructed depends on which valve it is and the severity of the damage. The tricuspid and mitral valves are the most commonly reconstructed valves.
Different reconstruction procedures are used depending on the type of valve damage.
Repair of tendons
Replacement or shortening of worn-out or weak valve tendons.
Used to treat heart valve stenosis. A balloon is inserted through a heart catheter all the way to the damaged valve, where it keeps the constricted valve open.
Removal of calcium deposits on the valve leaflets.
Separation of the valve leaflets if they have become thick or grown together.
Closure of a hole or tear in the valve using a tissue patch.
Ring-shaped implant that improves the tension of the valve leaflets.
Artificial heart valves
Artificial, mechanical heart valves consist of a hardened graphite core enclosed in a polyester ring. There are various models available. The most common model features an artificial valve made from two wings. The artificial heart valves are extremely reliable and have a very long, virtually unlimited service life. Therefore, they are used for younger patients. Modern mechanical heart valves do not react to magnet fields, so they do not cause any problems during MRI examinations (magnetic resonance imaging).
Biological heart valves
Biological heart valves are made from animal tissue. In general, there are two different types. The porcine valve, which is produced using the aortic valve wings of pigs, and the bovine valve, which is made from the pericardia of cows. The biological valves are chemically treated so that they are not rejected by the patient’s immune system. Compared to the artificial heart valves, biological heart valves have a limited service life and must be replaced after around 12 years. For this reason, biological heart valves are primarily used for older patients.
The third type of biological valves are human homograft heart valves, which are organ donations removed from human cadavers. These heart valves last longer than porcine or bovine heart valves. However, considering only a small number are available and the surgery is highly complicated, homografts are only used in special cases, such as for children.
What preparations are carried out before the operation?
A heart valve replacement generally requires open heart surgery, regardless of whether mechanical or biological heart valves are being transplanted. The operation is therefore performed under general anaesthetic. All the usual pre-operative assessments are required, such as a blood test, blood pressure measurement and an ECG. The patient may also have to stop taking blood-thinning medication. The patient is usually admitted to hospital on the day before the surgery. They should not consume food or drink before the operation.
For aortic valve replacements, older and seriously ill patients who face a greater operative risk can opt for cardiac catheterisation instead of open heart surgery. This method has been available now for several years.; It involves using a heart catheter to insert a folded biological valve.
The following information regarding the surgical procedure refers to open heart operations.
How is the operation performed?
The heart is accessed by separating the breastbone (sternum). During the operation, the heart is temporarily immobilised with the help of a special liquid solution (cardioplegia) and the patient’s circulation is maintained using a life-support machine. First the diseased heart valve is cut out, then a suitably sized replacement valve is selected and implanted. After the cardioplegic solution has been flushed out, the heart automatically starts beating again. While the patient is still in the operating theatre, the surgeon checks the functioning of the implanted heart valve by performing a transesophageal ultrasound examination (via the oesophagus).
If everything is working perfectly, the ribcage is closed. The operation usually takes two to three hours.
Over the last few years, a minimally invasive surgical technique known as a mini thoracotomy has become established, which does not involve separating the breastbone and opening the ribcage. This video-assisted method is primarily used to replace the mitral valve.
What is the success rate of this procedure?
The long-term results with mechanical valves are excellent. Most of the valves remain functional throughout the person’s entire life and do not need to be replaced. Biological valves develop calcifications over time and must be replaced after around 12 years.
What are the possible complications and risks of this procedure?
Overall, complications following heart valve operations are rare. As with all surgery, in exceptional cases the operation may lead to infections, nerve damage, post-operative haemorrhaging or blood clots (thromboses).
What happens after the operation?
People with artificial heart valves must take blood-thinning medication for the rest of their lives. This is accompanied by a higher risk of bleeding; however, if the person adheres to their treatment regime and avoids additional factors which can cause bleeding, this risk is only slightly higher than that of healthy people who have not undergone the surgery. People with biological heart valves only need to take blood-thinning medication for the first three months after the operation. People who have undergone this operation should avoid lifting heavy objects and major physical exertion until their wounds have fully healed. After the operation, the patient’s heart function is checked regularly over an extended period of time. Patients are also prescribed antibiotics for a certain period of time to prevent infections. From then on, antibiotics should be taken as a preventative measure whenever they are at risk of infection, for instance due to dental work.