Overview of Stentless Autograft/Homograft Aortic Valve Replacement
A valve is like a thin, movable sheet of tissue in your heart that makes sure blood only flows in one direction. When these valves don’t work properly or get too narrow, this can lead to various health problems. A type of heart disease called valvular heart disease, which affects the valves in the heart, is a significant health concern affecting about 2.5% of people. A common type of this disease is aortic valve disease, which includes aortic stenosis (narrowing of the valve) and regurgitation (backflow of blood).
When the aortic valve gets damaged, it can be managed with medication, a repair of the valve, or replacement of the valve using surgery or a technique called transcatheter aortic valve replacement. It’s important to choose the best method of valve replacement depending on several factors such as the patient’s age, their ability to tolerate blood-thinning medication, the risk of the valve getting damaged again, their blood clotting status, and plans for future pregnancies.
The valves used in aortic valve replacement can be mechanical or bioprosthetic (made from tissue). Mechanical heart valves can be disc, bileaflet (two-leafed), or ball-and-cage types. Bioprosthetic valves can come from animals (xenografts), the same species (homografts), or the same individual (autografts). Some bioprosthetic valves are put on a metal support or stent, or they can be attached directly to the aorta. Stentless valve replacements using tissue from the patient or the same species have become significant surgical options, offering certain benefits compared to traditional stented valves.
Even though putting a stent can reduce the space in the aortic valve and is not ideal for blood flow, it does not significantly impact the results of stentless valve replacements using tissue from the patient or the same species. This underlines the importance of considering how well the blood flows and other patient-specific factors when picking a valve replacement method. Furthermore, different types of bioprosthetic valves have similar rates of death and need for reoperation, emphasizing the need for care that is tailored to the individual patient. For patients who cannot have open-heart valve replacement surgery, a technique called transcatheter aortic valve replacement can offer a safer alternative. However, stentless valve replacements using tissue from the patient or the same species remain valuable options for many patients, especially younger individuals and those with certain clinical conditions.
Anatomy and Physiology of Stentless Autograft/Homograft Aortic Valve Replacement
The aortic valve is one of the four main valves in the heart and is located between the left pumping chamber (or Left Ventricle) and the large main artery that carries blood from the heart to the rest of the body (the aorta). It has 3 flaps, also known as leaflets, that are of varying sizes. These flaps are attached to a supporting ring (the aortic annulus), and open and shut to control blood flow. When the heart beats and pumps, the aortic valve opens to let blood flow from the heart to the rest of the body. When the heart rests between beats, the aortic valve closes to prevent blood from flowing back into the heart.
Aortic regurgitation (AR) is a condition where the aortic valve does not close tightly, causing blood to leak back into the heart chamber. This condition can be due to problems with the valve flaps themselves, such as if there are only 2 instead of 3, or if they wear out over time or become infected. In addition, certain medical conditions, such as Marfan syndrome and high blood pressure, can cause stretching of the main artery which can prevent the valve from closing properly.
The fact that blood is leaking back into the heart causes the heart to have to work harder than it should to pump enough blood to the rest of the body. Over time, this can cause the heart to enlarge and become less effective at pumping blood, leading to symptoms such as palpitations (feeling your heartbeat), tiredness, breathlessness, and in severe cases, heart failure.
The American College of Cardiology/American Heart Association (ACC/AHA) provides guidelines that categorize AR into 4 stages, based on the valve structure, how well it’s working, how the heart is responding, and symptoms. In Stage A, you are at risk for AR, but do not have significant valve problems. In Stage B, the disease is progressing, but you may not have symptoms. In Stage C, AR is severe, but you may still have no symptoms. In Stage D, AR is severe and you have symptoms.
Aortic stenosis (AS) is a disease characterized by the narrowing of the aortic valve, which limits blood flow from the heart into the body. This can be due to birth defects, age-related hardening of the valve, or scarring from an inflammatory disease like rheumatic fever. As the valve narrows, the left side of the heart has to work harder to pump blood, leading to an enlarged heart and potentially heart failure over time. Symptoms of AS can include chest pain, fainting, fatigue, and shortness of breath.
The diagnosis of AS starts with a physical exam and is confirmed with tests such as an echocardiogram (ECG), which uses sound waves to create pictures of the heart. Other useful tests may include a chest X-ray, which can reveal tightening of the aortic valve and changes in the size and shape of the heart, and cardiac catheterization, which can help evaluate any coexistent heart issues.
Similar to AR, the ACC/AHA guidelines categorize AS into 4 stages, based on the valve structure, how well it’s working, changes in the heart, and presence or absence of symptoms. Stage A is a risk for AS, with no symptoms. Stage B involves mild to moderate tightening of the valve. Stage C is severe tightening of the aortic valve without symptoms, whereas Stage D is severe tightening with symptoms.
Why do People Need Stentless Autograft/Homograft Aortic Valve Replacement
When the aortic valve in the heart isn’t working right, it might need to be replaced. The aortic valve controls the flow of blood from the heart into the aorta, a large blood vessel that carries blood from the heart to the rest of the body. This replacement procedure is called an aortic valve replacement.
There are different reasons a person might need an aortic valve replacement, such as aortic regurgitation and aortic stenosis.
In the case of aortic regurgitation, the aortic valve doesn’t close correctly which allows blood to flow backward into the heart. Initially, doctors usually try to treat this using medications. However, if the condition progresses and the heart gets damaged, a valve replacement might be necessary.
Aortic Stenosis, on the other hand, is when the aortic valve is narrower than normal. This forces the heart to work harder to pump out blood. It can often be managed with medications at first. However, if the situation worsens and the heart’s ability to pump efficiently decreases, a valve replacement surgery may be required.
In this replacement procedure, doctors have a choice about which type of valve to use. A bioprosthetic heart valve is generally preferred for specific situations, such as patients who cannot take blood thinners, patients who are at a lower risk for follow-up surgeries, those with future pregnancy plans, and those aged 65 or older.
Doctors also have what’s called autograft aortic valve replacement as an option. This involves using the patient’s own tissue to replace their aortic valve. Specifically, the patient’s pulmonary valve will be used to replace their aortic valve. This approach has the advantage that the transplanted pulmonary valve can grow and regenerate. The pulmonary valve, in turn, is replaced by a type of conduit (tube) made from animal tissue.
Homografts, which come from donors who have recently passed away, are another option for aortic valve replacements. They are commonly preferred in cases of aortic valve infection, especially if there is an abscess around the valve. They’re also recommended for patients who inject drugs and have a history of heart infections, as these patients have a higher risk for more surgeries. Xenografts, which come from animal tissue, are available in all sizes and is another type of conduit that can be used.
When a Person Should Avoid Stentless Autograft/Homograft Aortic Valve Replacement
The Ross procedure is a type of heart surgery. However, certain conditions can make it unsafe or impossible to perform the Ross procedure. These conditions include connective tissue diseases such as Marfan and Ehlers-Danlos syndromes, and inflammatory conditions like rheumatoid arthritis and systemic lupus erythematosus. These diseases can affect the pulmonary aorta or the pulmonary valve, parts of the heart that are crucial for this surgery.
Other situations when the Ross procedure may not be appropriate include when a person has multiple vessel coronary artery disease (a condition where the arteries that supply blood to the heart are diseased), a significant decrease in left ventricle function (the lower left chamber of the heart is not able to pump blood properly), or any existing pathology or issues with the pulmonary valve.
Homografts, which are heart valve grafts from human donors, are another option to replace the aortic valve. There aren’t really any specific situations where it can’t be done apart from if a suitable donor can’t be found, or if the patient or surgeon prefer another type of procedure. However, young patients might be advised not to have homograft valve replacement because as they grow, the valve might not fit properly anymore and they might need another operation in the future.
Equipment used for Stentless Autograft/Homograft Aortic Valve Replacement
If you’re having aortic heart valve replacement surgery, including the Ross procedure, it’s typically performed using a technique called open median sternotomy. This is when the surgeon opens up the chest to get to the heart. Before the surgery, the doctor will use a test called an echocardiography to check your heart valves. This test uses sound waves to create pictures of your heart so the doctor can see how it’s working.
During the surgery, the surgeon will use several important tools:
* The Hegar dilator: this is a device used to measure the size of the grafts (tissue used to replace your heart valve).
* Polypropylene sutures: these are like very strong threads used to attach the new valve securely in place.
* Dacron tube: this is used to extend the pulmonary valve (a heart valve that controls blood flow from the heart to the lungs).
* Cardiopulmonary bypass machine: this is a critical piece of equipment that keeps blood and oxygen circulating around your body while the doctor is working on your heart.
* Aortic cross-clamp: this tool is used to control blood flow by isolating the aorta (the main artery leaving the heart).
* Standard surgical instruments: these include common things like scalpels (surgical knives), scissors, forceps (tongs or tweezers), and needle holders.
Remember, your doctor and medical team are skilled professionals who will keep your safety and health at the forefront throughout the operation.
Who is needed to perform Stentless Autograft/Homograft Aortic Valve Replacement?
To replace a heart valve in a procedure known as an aortic heart valve replacement surgery, several specially trained healthcare professionals work together. This team includes a heart surgeon (someone who operates on the heart), an anesthesiologist (a doctor who ensures you’re comfortable and pain-free during the surgery), a cardiologist (a heart specialist), a surgery assistant (helps the surgeon during the operation), an operating room assistant (helps prepare the operating room), a radiologist (a doctor who uses imaging techniques), and nurses (take care of you before, during and after the procedure). Additional staff members are also present to ensure your safety and care throughout the surgery.
Preparing for Stentless Autograft/Homograft Aortic Valve Replacement
The main purpose of getting ready for the surgery is to make sure everything is clean and sterile. Before the process begins, doctors will shave and cleanse the patient’s chest. They will then cover the patient according to the rules of the hospital. The patient will also be prepared for general anesthesia, which is a type of medicine that puts you to sleep during the procedure. Doctors will also mark important areas on the body, like the jugulum and xiphoid process (these are points in the neck and lower chest), so they know where to operate.
How is Stentless Autograft/Homograft Aortic Valve Replacement performed
The Ross procedure is a type of open-heart operation to replace the aortic valve – a valve in the heart controlling blood flow to the rest of the body. In this procedure, the surgeon removes your damaged aortic valve and replaces it with your own pulmonary valve. This replacement valve is often called an autograft. The pulmonary valve, which originally controlled the flow of blood from your heart to your lungs, is then replaced with a donor valve. This operation is performed through an incision in the middle of your chest, a surgical technique known as a median sternotomy.
First, the surgeon stops the heart to protect it from damage during surgery. This step is called cardioplegia. The organ is then cooled using intermittent techniques, and warmed again before continuing with the procedure. The surgeon will then inspect and remove the aortic and pulmonary valves. Particular attention is given to the positioning and paths of the coronary arteries during these steps.
The surgeon then removes the pulmonary valve without damaging it and ensures the critical heart artery associated with it, the first septal coronary artery, is well preserved. After the diseased aortic valve is removed, the size of the ring that secures the valve to the heart is checked to make sure it matches the new graft size. Sometimes additional procedures are necessary to adjust this ring size. The autograft valve, which is your pulmonary valve, is then inserted into the position originally occupied by your aortic valve and secured with special stitches, also known as sutures.
Next, the surgeon takes care of reattaching your coronary arteries, starting with the left coronary artery. The replacement of the pulmonary valve which was removed earlier with a donated valve takes place next. The final stages of the procedure involve further insertion of the replacement graft and securing it in place.
In a homograft aortic valve replacement, a surgeon also uses a median sternotomy to access the heart. The heart is stopped again to protect it during the surgery. The surgeon then removes any infected tissue and your damaged aortic valve. Sometimes, this can make a hole in the area where the aortic valve and the mitral valve touch, the mitroaortic junction. The hole is patched up using part of a leaflet from the graft or from the mitral valve. Finally, the top of your heart, the atrium, is stitched closed and any additional patches of the heart’s covering, the pericardium, are put in place if needed.
Possible Complications of Stentless Autograft/Homograft Aortic Valve Replacement
About 30% of people who go through the Ross procedure, a type of heart surgery, might notice changes in a part of their heart called the pulmonary autograft. Those under 25 usually require another surgery on the autograft during their lifetime and are more likely to see degeneration of their right ventricular outflow tract, a part of their heart. Older people have a 32% to 68% risk of needing another surgery due to graft valve-related problems with their heart.
However, the Ross procedure has comparatively lower rates of bleeding, clotting and inflammation of the heart lining complications than other similar operations. It also has fewer complications related to early and late mortality.
The Melbourne group, a team with significant experience, uses a method where the patient’s own aorta, a major blood vessel leaving the heart, supports the pulmonary autograft. The group studied the long term outcomes for the technique and found that these autograft dimensions remained stable for up to 15 years after surgery. Only 1.5% of patients showed an increased size in their aortic root over 40 mm, with none going over 43 mm. However, those with preoperative AR, a heart-related condition, and those with a large aortic annulus, the exit of the aorta, had a higher risk of enlarging this area of the heart and needing additional surgeries. Despite these risks, about 96% of these patients did not require a second surgery after 18 years.
Another type of operation called homograft aortic valve replacement may lead to death, but this is rare. Structural changes may occur in the graft roughly 20 years after the operation due to ruptures, calcification or poor leaflet coaptation. The ARISE trial, which studied this, showed outcomes similar to another study with about 36% of the patients included in both. Tricks also included 38% young patients, which lowered the average age to 28.7 years. The trial reported a very low rate of adverse events with similar rates of freedom from mortality, heart inflammation, reoperations, bleeding and blood clots to the other study.
Five years after the procedure, the numbers are quite promising, with more than 90% of patients free from these complications. This includes mortality (98.2%), endocarditis (97.3%), re-operations (90.8%), bleeding (99.5%) and blood clots (99.5%).
What Else Should I Know About Stentless Autograft/Homograft Aortic Valve Replacement?
Valvular heart disease is a condition that affects the valves of the heart, impacting about 2.5% of people around the world. Two specific types, aortic stenosis (AS) and aortic regurgitation (AR), make up a large amount of these cases. Aortic stenosis, which is more common in older people, affects 0.2% of people in their 50s, and this increases to 9.8% for those between 80 to 89. There’s a type of birth defect in the heart valve known as a bicuspid aortic valve, which affects 0.5% to 0.8% of the population and often needs a surgical fix in younger patients around 50 years old. Aortic regurgitation is another valve problem which affects 0.5% of the population, and like AS, it also becomes more common as we age.
There’s a procedure called the Ross procedure that’s been around for more than 50 years. It’s often a topic of debate among medical professionals for treating adults, but there’s plenty of evidence to highlight its benefits. The main advantages are that it tends to provide better survival rates, removes the need for blood-thinning medication, there’s less chance of heart infection and not much need for additional surgeries later on. One of the reasons for these benefits is that it uses a person’s own heart tissue which keeps the natural function of the valve and responds well to body signals, leading to a better blood flow and overall better quality of life. Especially for children and younger patients, the Ross procedure seems to offer better results compared to other types of graft operations.
Another procedure called homograft aortic valve replacement, where a valve from a donor is used, can be a little complicated but also offers good results, especially for adults and patients planning to have children. Decellularized homografts, where the donor cells are removed to decrease immune response, appear to last longer compared to the traditional way of preserving the grafts, particularly beneficial for younger patients. In one study from 2016, more than half of the patients who had a decellularized homograft were free from repeat surgeries after 10 years. Longer term follow-ups are important to accumulate more results on these graft procedures to confirm their effectiveness.
Decellularized homografts seem to also have an additional advantage by not causing much immune system reaction. This makes them a good option for patients who may also need an organ transplant later.