Overview of Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement
Given that the heart beats around 80 times per minute, for over 70 years, which adds up to over 3 billion beats, it’s quite impressive that heart valves work so well. Considering all this activity, less than 2% of people are estimated to have issues with their heart valves, also known as valvular disease.
The history of treating heart valve disease is filled with brave innovations and teamwork across different medical fields. Over time, treatments have evolved from quite primitive methods like inserting a surgeon’s finger through a heart valve, to sophisticated techniques like the creation of artificial heart valves. Even something as simple as treating strep throat with antibiotics has had an impact, by preventing a type of heart valve disease called rheumatic heart disease from developing in the future.
However, for this article, we will focus on a specific surgical treatment called surgical aortic valve replacement (SAVR), which is used for problems like narrowing (stenosis), leakage (insufficiency), or infection (endocarditis) of the heart valves. In this procedure, a bioprosthetic valve, which is an artificial valve made from tissue, is used to replace the problematic valve.
If you’re interested, you can also learn about similar treatments, especially those related to the replacement and repair of the aortic valve. These include procedures like the Ross procedure, minimal invasive aortic valve surgery, and transcatheter aortic valve replacement (TAVR), as well as general information about aortic valve disease and artificial heart valves.
Anatomy and Physiology of Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement
The aortic valve is a very important part of the heart. Its job is to keep the blood flowing smoothly from the left part of the heart to the main blood vessel, the aorta. This area is very sensitive and needs to be able to handle big changes in pressure as the heart pumps blood.
The aortic valve area is loaded with details. As the blood moves from the left part of the heart, it first passes through the ventriculo-aortic junction (VAJ) which is where the heart tissue turns into the aorta tissue. If you look at pictures of this part of the heart, the VAJ is like the lines that connect the points of the valve flaps (also known as leaflets). As you continue to explore this area, you’ll see where the flaps are connected to the aortic tube. This section is referred to as the basal ring or surgical aortic annulus. It’s not a perfect oval shape because each valve leaflet differs slightly. This gives more space for the heart to adjust and pump efficiently.
As we continue our exploration, after passing through the valve flaps, we see the top points of their attachments marked as a ring, known as the sinotubular junction (STJ). This marks the end of the aortic root and the beginning of the ascending aorta. Backtracking our journey, we notice that under this unique formation, each valve leaflet contains a small hollow space. These are known as sinuses. In the right sinus, there is the origin of the right coronary artery; in the left sinus, there is the origin of the left coronary artery; the third sinus (the posterior one) contains no coronary artery. Sometimes, these coronary origins can be slightly different in 1% of the population.
The shape of the sinuses collect what’s called ‘eddy currents’ which keep the valve from sticking to the aortic wall. This mechanism helps the blood flow to and from your heart smoothly. The valve flaps are made of special cells which keep them functioning correctly.
The aortic valve is located near some very vital parts of your heart that doctors take into consideration during surgery. These include the non-coronary and the left coronary cusps of the aortic valve, that are structurally contiguous with the central fibrous body of the heart, the anterior leaflet of the mitral valve, and several others.
The two main issues that can occur with the aortic valve are known as stenosis (tightening of the valve) and insufficiency (or regurgitation – leaking of the valve). Both of these conditions can lead to complications, such as causing stress on the heart which may lead to other medical problems.
Aortic stenosis is commonly caused by aging and heart disease. Most of the time, it requires a replacement of the aortic valve. Meanwhile, aortic insufficiency is found less frequently and can be caused by a variety of health issues including those affecting the heart’s tissues, arteries, or even infections. Depending on the patient’s specific situation, it may need to be corrected by replacing or repairing the aortic valve.
Why do People Need Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement
Valvular heart disease (problems with the valves in your heart), can be difficult to diagnose because patients may not show any overt signs or symptoms. For instance, if a person has a condition called aortic stenosis, that person may not even show any symptoms at the time of detection, but tragically, could die within two years if left untreated. Hence, it’s really crucial to determine when and if a patient needs any intervention or treatment.
In order to do this, the American College of Cardiology (ACC) and the American Heart Association (AHA) put together some guidelines that help doctors understand when and if a patient needs any medical treatment for this disease. The stages of valvular heart disease range from A to D, and are determined by the results of an ultrasound of the heart (echocardiography). Each stage has various indications dictating if and when a patient should be treated.
For patients with stage A of the disease, a screening ultrasound is usually done. If the disease has progressed to stage B, patients would need check-up ultrasounds every 3-5 years. When the disease reaches stage C, patients would need ultrasound surveillance every six months to a year along with possible intervention. Patients at stage D typically require immediate attention and treatment.
Now, let’s talk about two specific conditions, aortic stenosis, which is when the aortic valve in the heart tightens up, and aortic insufficiency, when the aortic valve fails to close tightly. In both cases, treatment depends on the severity and symptoms that patients are experiencing. These are usually divided into two classes:
– Class I patients: In this situation, treatment is usually needed if the patient is displaying symptoms and severe parameters based on echocardiography, that include significant narrowing of the aortic valve, high pressure gradient, or high jet velocity for aortic stenosis, or severe regurgitation and failure of the left ventricle for aortic insufficiency. Treatment might also be needed if the patient is scheduled for some other heart surgery, or if the heart’s pumping strength (ejection fraction) is less than 50%.
– Class II patients: These include patients with very severe parameters without symptoms, reduced exercise tolerance, anomalies in the frequency or pressure of their heart’s activity, and a few others.
Once the doctor determines that an intervention is necessary, they will evaluate the risks associated with surgery or intervention. This is done using a combination of risk calculators, frailty indices, and assessing the patient’s overall health and other existing conditions.
Once the intervention method is selected, the next step is to decide between a valve repair or replacement. This choice depends on the type and severity of the disease and the expertise available. If a replacement is needed, there are three options: mechanical valve, bioprosthetic valve, and stentless pulmonary autograft/homograft. Each option has its own requirements for blood-thinning medications and durability.
Lastly, it’s essential to remember that the surgical treatment of another serious condition called infective endocarditis (an infection of the heart valves) needs to be tailored to each patient’s specific condition. Generally, a full course of antibiotics should be the first step. If the infection persists or the patient’s condition deteriorates, the doctors might consider a surgical intervention.
When a Person Should Avoid Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement
Research has shown that any kind of treatment on pregnant women who have a narrowing or malfunction of their heart valves, even in advanced stages (stage D), can be harmful. Such treatment should only be considered if the woman is experiencing severe, unstoppable heart failure. If a woman is at stage D of this illness, any treatment should be done before she gets pregnant. It’s also been noted that biological heart valves, those made from animal or human tissue, can break down quicker during pregnancy, so they’re not recommended for women who might become pregnant.
Warfarin, a common medication for treating heart problems, can cause birth defects if taken during the first three months of pregnancy. However, there are many different medication strategies that can be used to protect both the health of the mother and her unborn child if the woman has a mechanical (artificial) heart valve.
Just like situations with pregnant women, those with a high or extremely high surgical risk should not be offered a heart valve surgery known as SAVR. If a patient develops an infection in the heart (infective endocarditis) and needs surgery, only a minimal amount of foreign material should be used. While replacing the infected heart valve with a biological one is not outright inadvisable, a homograft (a graft that uses human tissue) which can resist infection better may be preferable.
If a patient gets a stroke because the infection in the heart (septic emboli) has travelled to the brain, then heart surgery should be put on hold. Ideally, after a stroke caused by an interruption of blood flow to the brain (ischemic stroke), surgery should be delayed by two to three weeks and after a stroke caused by bleeding in brain (hemorrhagic stroke) for four weeks.
Some people may not want a biological heart valve as it may be conflicting with their religious beliefs. They may not agree with the use of biological heart valve due to it containing bovine (cow) or porcine (pig) components.
Preparing for Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement
If you have heart valve disease, your doctor will usually start by asking you about your medical history and doing a physical examination. They will also likely need to do a chest X-ray and a certain type of ultrasound called a transthoracic echocardiogram (TTE), which allows them to see your heart and how it’s working in more detail. This TTE uses 2-D imaging and something called Doppler technology to measure the speed and direction of blood flow within your heart.
Depending on what the doctor finds, they may also use other types of examinations, such as a transesophageal echocardiogram (TEE), a computed tomography angiography, a cardiac magnetic resonance imaging, or a cardiac catheterization. These are all high-tech imaging techniques that give different types of information about your heart and how it’s functioning.
Before any treatment decisions are made, your doctor will talk with you about your preferences when it comes to your heart valve. This is because there are often different treatment options available, and it’s important that you have a say in the care you receive.
How is Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement performed
The standard method of replacing an aortic valve involves open-heart surgery. This procedure is traditionally carried out by making a large incision down the middle of the chest and using a device to take over the role of the heart and lungs (a process called cardiopulmonary bypass or CBP), letting the surgeon operate while the heart is stopped. A newer, minimally invasive method called Transcatheter Aortic Valve Replacement (TAVR) is also now available.
In both procedures, the blood flow is diverted away from the heart to the CBP machine via tubes inserted into the heart and major blood vessels. The surgeon ensures that the heart’s blood supply (coronary ostia) is accurately identified and well supplied with blood, especially when the patient has unusual heart structure (like bicuspid valves). A technique called cardioplegia is often applied, which uses a solution to stop the heart and preserve it during surgery.
Once the patient is prepped for surgery, the surgeon starts to replace the aortic valve. After removing the patient’s original valves, the new artificial valve is sewn into place using a strong thread. The surgeon makes sure the replacement valve is properly fitted with no gaps that could cause leaks. The heart is then free of air and the clamp on the aorta is released. The patient is gradually taken off CBP, the tubes are removed, and the chest is sutured closed.
In terms of choosing a suitable artificial valve, the surgeon has to pay close attention to its size. Since each brand manufactures different sizes, the goal is to choose the largest size that the patient’s heart can accommodate. This is to avoid a phenomenon called “patient-prosthesis mismatch” (PPM). This happens when the artificial valve is too small relative to the patient’s body size. If the mismatch is severe, it may lead to residual pressure and the heart might not get all the benefits of the surgery.
The longevity and performance of the artificial valve can also vary. Mechanical valves usually last longer and work better than biological (tissue) valves, but this difference has been reducing with the introduction of newer designs. Bioprosthetic valves can sit either inside or on top of the annulus (base of the valve’s position) with the ones on top usually performing better. But all biological valves, whether made from pig or cow tissue, eventually become hardened (calcified).
If the patient’s annulus is very narrow, making it hard for a valve of suitable size to be implanted, the surgeon can perform an enlargement procedure. This involves cutting open the aorta and sewing in a patch to increase its size, allowing for a larger valve to be implanted.
Possible Complications of Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement
The American Association of Thoracic Surgeons and the Society of Thoracic Surgeons created a committee to establish standard definitions related to artificial heart valve complications in order to compare different types of heart valves. One of their definitions is about the differences between mortality in hospital and mortality within 30 days after surgery. The committee also categorizes complications and morbidities associated with heart valves.
One category is “Structural valve deterioration” (SVD). This is when the valve develops problems like becoming too calcified (hardened), breaking, tearing or not being secured properly by the sutures. However, SVD does not include problems like infection (prosthetic valve endocarditis) or the formation of clots (thrombotic dysfunction); these issues have their own categories.
Another category is “Nonstructural dysfunction”. This refers to issues not caused by the valve itself like obstruction due to the wrong position of the valve, leakage because the valve is the wrong size, and hemolytic anemia, a blood disorder that can result from the leakage. There’s also the “Bleeding event” category which is any event causing hospitalization, the need for a blood transfusion, or death, but isn’t connected to blood-thinning drugs.
A study presented the frequency of these complications for a heart valve that isn’t available anymore as follows:
- Structural valve deterioration – 0 events per patient per year
- Nonstructural dysfunction – 0.2 to 0.8 events per patient per year
- Clotting events – 0 to 0.2 events per patient per year
- Blood clot traveling to other parts of the body events – 1.4 to 2.5 events per patient per year
- Bleeding events – 0.8 to 2.5 events per patient per year
- Heart valve infection events – 0.4 to 0.7 events per patient per year
- Needs another operation – 0.3 to 1.8 events per patient per year
In contrast, a different study showed that after 12 years, for biological heart valves placed in the aorta, 87% of patients did not face valve-related deaths, 84% did not need another surgery, 93% of people over 60 years old and 76% of people under 60 years old didn’t need the valve replaced due to Structural Valve Deterioration.
For another biological heart valve placed in the heart’s mitral valve position over 25 years, the rates were: blood clot formation – 0.5% per valve per year, bleeding event – 0.7% per valve per year, heart valve infection – 0.4% per valve per year, and structural valve deterioration – 2.3% per valve per year. Structural valve deterioration is the most common reason why biological valves need to be replaced, especially after 7 or 8 years. After 10 years, between 70% and 90% of patients are free from structural valve deterioration, while after 15 years, it’s between 50% and 80%.
What Else Should I Know About Bioprosthetic Stented Pericardial Porcine Aortic Valve Replacement?
Aortic valve disease is a serious health condition that, if not treated, can lead to serious outcomes. The aortic valve is a crucial part of your heart that controls the flow of blood out of the heart and into the aorta, your body’s main artery. When the valve isn’t working properly, it can restrict blood flow (aortic stenosis) or allow blood to leak backwards (aortic insufficiency). Both of these problems put extra strain on the heart.
Severe aortic stenosis, even if you bave no symptoms, can significantly reduce your chances of survival to 38-83% in 5 years. If symptoms appear, then you have an increased risk of sudden cardiac death by 2% every month. Aortic insufficiency is less critical but still quite serious. For patients with no symptoms, the survival rates are 75% and 60% at 5 and 10 years respectively. However, if symptoms occur, there is a 10% risk of death every year.
Due to these risks, surgical aortic valve replacement (SAVR) is considered a lifesaver. This surgery involves replacing the damaged valve with a replacement, which can be a mechanical or biological (bioprosthetic) valve. The average risk of dying within 30 days of this operation is recorded to be at 3.4%. Mechanical valves and biological valves have shown 15-year survival rates of 66% and 79%, respectively. With technological advancements since the 1970s, these numbers are expected to be even better today.
But surgery doesn’t only increase survival; it provides other benefits too. Following surgery, the left side of your heart, which usually gets overworked due to valve disease, starts to recover and return to normal size 18 months to 5 years post-operation. Also, 70-90% of patients who had heart failure symptoms prior to surgery see a significant reduction in their symptoms. Most report feeling as healthy as someone with no heart disease at all, a state that can last for at least 10 years post-surgery.
