Overview of Pulmonary Artery Banding
Pulmonary artery banding (PAB) is a type of surgery used primarily to improve symptoms of certain birth heart defects. It’s usually used when there’s too much blood flowing to the lungs from the heart due to something we call a “large left-to-right shunt”. This means there’s an abnormal connection causing blood to flow from the left side of the heart to the right, resulting in an overload of blood to the lungs.
There was a time when infants with some kinds of heart defects would have PAB surgery as their first operation. However, these days the use of PAB is generally limited to a specific set of infants who have complicated heart defects. This is because surgical techniques have greatly advanced and directly repairing the defect has seen improved success rates.
PAB surgery works by protecting the blood vessels in the lungs. It cuts down on excessive blood flow and reduces the pressure on the lungs, which in turn helps prevent damages to the lung vessels and from developing a condition called pulmonary hypertension, which is high blood pressure in the lungs. In some cases, PAB surgery is performed to help prepare a part of the heart called the left ventricle for another planned surgery. This part of the heart might need “training” to work as the main pumping chamber in the future.
The credit for the first PAB surgery goes to Muller and Dammann who performed it in 1951 on a baby with a large hole in the wall between the lower chambers of the heart (called a ventricular septal defect or VSD), and a large left-to-right shunt which caused an overload of blood flow to the lungs.
Following this, many studies have shown that PAB surgery can be helpful in patients suffering from congestive heart failure – a condition where the heart can’t pump enough blood to meet the body’s needs – due to several heart defects. Although the use of PAB has declined among surgeons, it remains a crucial tool for those treating complex heart defects in children.
Anatomy and Physiology of Pulmonary Artery Banding
The pulmonary artery banding procedure might be considered as a possible method to ease heart issues, among other treatments. To do this, doctors look at a few important factors. It’s essential to examine the size of the main pulmonary artery (MPA), the artery that carries oxygen-poor blood from the right side of the heart to the lungs. The band should be placed in the middle of the MPA to avoid affecting the parts of the artery nearby.
The right pulmonary artery (the one on the right part of your heart) generally starts slightly earlier and more abruptly than the one on the left. Therefore, if the band inadvertently moves distally, it may have a higher chance of causing distortions or damage to the right artery. However, similar damage can also occur to the left artery. Another issue to consider is that the MPA, due to its higher blood flow ratio when compared to the aorta, tends to be larger and more fragile, increasing the risk of the vessel wall rupturing during the operation.
Patients with a large hole in the lower chamber of their hearts, known as a ventricular septal defect (VSD), and low pulmonary vascular resistance, will experience high levels of blood flow to their lungs. This condition is called pulmonary over-circulation, evident in symptoms such as fast breathing, difficulty feeding, and fluid build-up in the lungs. Doctors can skirt these symptoms short term by providing diuretics, afterload reduction, and supplemental feeding methods. Nonetheless, if this over-circulation continues for an extended period, it may result in irreversible vascular changes, leading to medial thickening of the vessel walls and the development of pulmonary hypertension, particularly in cases of high blood flow and high pressure.
During a pulmonary artery banding procedure, doctors will place a band around the MPA to slow down blood flow to the lungs. This can potentially balance the blood flow between left to right, reducing the amount of blood heading toward the lungs. By doing this, the procedure protects the lung’s blood vessels from being exposed to potentially harmful high pressures, thereby avoiding harmful changes to the vessel structures. Consequently, it will also increase the amount of blood flow to the rest of the body and raise blood pressure levels. However, in some heart defects where it’s crucial to maintain a mix of blood with normal oxygen levels, employing PAB might not work, especially if the defect includes a restricted atrial septal defect. Additional procedures might be required to widen or remove this blockage.
Why do People Need Pulmonary Artery Banding
Pulmonary artery banding is a surgical procedure that is performed for mainly two reasons:
1) To reduce the flow of blood to the lungs in patients who have an abnormally high amount of blood flowing to their lungs due to a condition “left-to-right shunting”. This is typically a temporary solution meant to prepare the patient for a more extensive surgery in the future.
2) To put more pressure on the left ventricle (a part of the heart that normally pumps blood to the lungs) to prepare it to pump blood to the rest of the body. This is typically done for patients with a condition known as transposition of the great arteries (TGA), a heart defect where the two main arteries leaving the heart are swapped in position.
There are several situations where reducing the blood flow to the lungs might be necessary. These include cases where the patient:
1) Has multiple small defects in the muscle of the heart, which may be hard to fix surgically, especially in babies.
2) Has one or more such defects along with other health problems (e.g., very low birth weight, infection, pneumonia, brain bleeding, failure of multiple organs) that complicate surgery.
3) Has a complicated defect of the heart valves, which can be temporarily managed before committing to a full repair after the patient grows and develops more.
4) Is a high-risk newborn with under-developed left part of the heart; in such cases, blood flow to the lungs is typically managed using pulmonary artery banding and another procedure to keep a certain blood vessel (ductus arteriosus) open.
There are also several situations that require enhancing the function of the left ventricle. For instance, in patients with D-TGA who presented late (>1month) or in patients with L-TGA, the left ventricle needs to be prepared, or “trained”, for a future heart-switching operation because the left ventricle has been functioning as a low-pressure ventricle and might not be conditioned to handle higher pressure. This procedure is also used to reduce problems with the tricuspid valve in patients with L-TGA without VSD by putting pressure on the left ventricle, which causes the heart wall between the two ventricles to move and improve closure of the valve. In patients with only one functional ventricle and blood flow to the lungs, this procedure is used in conjunction with another procedure called the Glenn shunt to maintain some blood flow but also keep blood pressure low in a major vein called the superior vena cava.
When a Person Should Avoid Pulmonary Artery Banding
There are a few situations where it might not be possible to perform a medical procedure known as pulmonary artery banding (a surgery to limit blood flow to the lungs). Let’s break these down:
1) Infants who have certain types of heart defects, like double inlet left ventricle or tricuspid atresia with TGA risk potential future blockage under the aorta, the main artery in the body, need to avoid this surgery. The reason being that pulmonary artery banding can sometimes cause parts of the heart to grow bigger, which could worsen the blockage in the aorta.[20]
2) Patients who already have a high pressure across their aorta or area below it. The problem here is that doing this surgery might end up creating two areas of high pressure – both in the aorta and in the pulmonary artery (the vessel supplying the lungs). This could put too much stress on both chambers of the heart that pump blood.
3) If a valve in the heart (the AV valve of either the lung or systemic part) is severely ‘leaky’ or regurgitating, the surgery might worsen this problem. That’s because it increases the amount of work the heart has to do, and so is often not recommended.
4) Individuals with Truncus arteriosus, a rare kind of heart defect. Various features of this condition make banding the pulmonary artery difficult and unpredictable, and so the surgery is often avoided in these patients.
Who is needed to perform Pulmonary Artery Banding?
A team made up of different types of healthcare workers is involved in heart surgery and care. This team includes heart surgeons, doctors who specialize in children’s heart conditions, doctors who give medications to make you sleep during the surgery (anesthesiologists), nurses who work in the operating room and intensive care unit, and professionals who operate a heart-lung machine during the surgery (perfusionists). They all work together to plan the surgery, help during the procedure, and take care of you after the surgery.
Preparing for Pulmonary Artery Banding
Before surgery, it’s recommended that patients get an echocardiography. This is a type of test that uses sound waves to create detailed images of the heart, helping doctors identify any potential issues. In complex cases, other imaging tests like magnetic resonance imaging (MRI) or cardiac catheterization may be required, but these aren’t usually necessary for simple heart conditions, such as a ventricular septal defect (VSD), which is a hole in the wall separating the heart’s two lower chambers.
The goal before surgery is to minimize the flow of blood from the left side of the heart to the right side by reducing the pressure in the arteries and also by using medications to remove excess fluid from your body. This is very important, especially for patients who show signs of congestive heart failure, a condition where the heart can’t pump blood as well as it should.
In severe cases, where too much blood is going to the lungs, breathing assistance may be needed. Machines will help to ensure that these patients get enough oxygen and are able to breathe properly, particularly if there is fluid build-up in the lungs.
However, there needs to be a balance. Doctors must be careful not to give these patients too much oxygen because oxygen can expand the blood vessels in the lungs, which would allow even more blood to flow to the lungs.
How is Pulmonary Artery Banding performed
Surgeons can opt for various ways to perform pulmonary artery banding (a procedure to limit the amount of blood flow to the lungs). These could include making an incision in the front or side of the chest, or through the middle of the ribs. The choice depends on the patient’s condition and what other surgeries might need to be done.
The process of the surgery involves the surgeon gaining access to the aorta (the large blood vessel that carries blood from your heart to your body) and the Main Pulmonary Artery (MPA – the artery transporting blood from the heart to the lungs). Then, a band is prepared and placed in the optimal location. Different materials can be used for the band, but a tape made from the tissue of the umbilical cord has been found especially effective due to its low risk of eroding the vessel wall (the structure enclosing the blood vessel). It can also be made adjustable by passing it through a rubber snare.
Trusler’s formula – a calculation created by medical professionals – is used to determine the right size of band needed. The end size will depend on several factors: the pressure gradient of the band, the pressures downstream of the pulmonary artery, and potentially the level of oxygen saturation if the patient has a particular heart condition known as a single ventricle.
After that, the band is carefully placed around the MPA, avoiding the section of the MPA making up the pulmonary valve and branch pulmonary arteries. This helps avoid unpleasant outcomes, such as a distortion of the pulmonary valve or impingement of the branch arteries. The band is then secured, and the size of the band can be adjusted after the operation by adding or removing medical clamps.
On occasion, due to resorption of folds in the MPA, the band may become loose over time. If that’s the case, an additional procedure can be performed involving an incision of the MPA before the band placement to correct this issue. Following the surgery, the surgeon will aim to achieve specific cardiovascular levels including certain blood pressure measures in the pulmonary artery, and oxygen saturation levels.
Eventually, when further surgeries are done and everything has healed well, the band could be removed. It often shows signs of a narrowing in the MPA. To fix this, the surgeon may need to remove the narrowed part and stitch the ends together, or make an incision and augment this segment with a patch. If the band had only been in place for a few months or less, then an operation to widen the narrowed segment may not be necessary.
Possible Complications of Pulmonary Artery Banding
Pulmonary artery banding, a type of heart surgery, can sometimes have complications or side effects, these might include:
1. Narrowing or distortion of one or both of the branch PAs, which are the vessels that carry blood away from the heart to the lungs.
2. Changes in how the pulmonary valve, which controls the flow of blood from the heart to the lungs, functions.
3. Pressing against the circumflex artery, a major blood vessel near the heart.
4. The band used in the surgery might wear through the wall of the pulmonary artery.
5. Formation of a pseudoaneurysm, a ballooning of the artery wall, in the pulmonary artery.
6. Hemolysis, which is a condition where red blood cells break down faster than the body can produce new ones.
7. Thrombosis, a condition where blood clots form in the blood vessels.
8. The band could be placed in a way that leads to changes that can’t be reversed in the pulmonary vasculature, the network of vessels in the lungs, resulting in high blood pressure in the lungs, also known as pulmonary hypertension.
9. Infection at the site of the surgery.
What Else Should I Know About Pulmonary Artery Banding?
Successful Pulmonary Artery Banding (PAB), a type of heart surgery, often leads to a significant improvement in heart health. Specifically, it can improve the fluid balance in the heart, ease the symptoms of congestive heart failure (a condition where your heart has trouble pumping blood), improve blood flow in the lungs, and reduce the amount of blood in the heart when it’s relaxed (at the end of filling up). The death rate among patients undergoing PAB is usually due to any complex heart defects they have, not the surgery itself.
Patients undergoing PAB are often those who are seen as high-risk for more complex heart repair, due to their severe heart problems. Therefore, early reports showed about 25% of patients undergoing PAB did not survive. However, the survival rates have gotten much better with advances in surgical methods, better timing of the surgery, and improved care after the surgery. The more recent reports have shown that the death rate has dropped to about 5%.
