Overview of Catheter Management Pulmonary Valvular Disorders
Due to advancements in specific areas like children’s heart health and surgery, the condition known as congenital heart disease is now more commonly seen in about 1 in 150 adults. Roughly half of these adults had surgery as children to address this. There is a high chance that these individuals may need additional surgeries or interventions later in life.
In about 20% of newborns with this condition, a part of their heart called the ‘right ventricular outflow tract’ is affected. This can be due to different kinds of defects like tetralogy of Fallot, truncus arteriosus, and pulmonary atresia. To manage these issues, various methods like using bio-prosthetic valves, patches, and small tubes known as conduits are used to help connect the right part of the heart to the pulmonary artery.
In some cases, when there’s an unusual left anterior descending artery coming from the right coronary artery that crosses the outflow tract, these conduits become necessary. These conduits help to return the function of the pulmonary valve back to normal. However, challenges such as the conduits hardening or narrowing can arise and this results in the need for additional interventions.
Many factors contribute to these challenges. These include the patient’s age, the nature of the heart defect, the type of tissue used in the procedure, the specific intervention performed, and the materials used in that intervention. For instance, deterioration of the transplanted valve can lead to problems in the right ventricular outflow tract and issues like pulmonary regurgitation and pulmonary stenosis. It’s estimated that about half of these patients will need another intervention.
Moreover, the prospect of a repeated surgery can carry risks like chest adhesions, problems with blood supply to the heart, heart failure, and issues affecting multiple organs. Earlier surgical attempts to manage tetralogy of Fallot resulted in complications. This includes insufficient function of the pulmonary valve, stretching of the tricuspid valve leading to reverse blood flow (regurgitation), and abnormal heart rhythms that could lead to sudden cardiac death.
A significant development in the treatment has been a procedure called transcatheter intervention, which involves the use of a balloon to widen the artery and a stent to hold it open. Despite its tremendous advantage, there can still be significant pulmonary regurgitation.
Today, a less invasive approach called Transcatheter pulmonary valve implantation is commonly used for adults with congenital heart disease. This procedure helps restore the function of the pulmonary valve earlier, potentially preventing irreversible damage and dysfunction. This could potentially reduce the number of surgeries needed across a patient’s lifetime.
Anatomy and Physiology of Catheter Management Pulmonary Valvular Disorders
The best physical structure for a procedure known as transcatheter pulmonary valve implantation (TPVI) is when the tube that goes from the right ventricle of the heart to the start of the lungs (RVOT) is the same size all the way to where the pulmonary artery splits into two. It’s helpful if the main pulmonary artery is long enough so it doesn’t have to be propped open at the split off. Right now, TPVI is mainly suggested for use when the tube from the RVOT isn’t working properly and if it is larger than 16 millimeters. Sometimes, these valves are used in a way that isn’t officially approved in patients who have either their original heart structure or have had a certain type of heart repair surgery, or in those with tubes smaller than 16 millimeters.
Why do People Need Catheter Management Pulmonary Valvular Disorders
Deciding the best time for an intervention on the right ventricular outflow tract (RVOT), which is part of the heart, can be a bit difficult. There are currently guidelines that help specialists decide when to perform a procedure called transcatheter pulmonary valve implantation (TPVI). TPVI is a kind of treatment that helps fix problems with the pulmonary valve, a vital valve in the heart. The guidelines used consider different factors like: how well the heart is pumping blood, if there’s a blockage in the RVOT, if there are abnormal heart rhythms, and other possible heart defects.
This procedure, TPVI, can be used to help patients who do not have symptoms but do have advanced heart disease. Here are some situations when it might be needed:
1. The right side of the heart is significantly larger than it should be: this can be measured by something called Right Ventricular End-Diastolic Volume Index (RVEDVI) being more than 150 ml/m2 or Right Ventricular End-Systolic Volume Index (RVESVI) being more than 80 ml/m2.
2. There is a decrease in how well the right side of the heart is pumping blood: this is measured by something called Right Ventricular Ejection Fraction (RVEF) being less than 45%.
3. If the heart has persistent abnormal rhythms.
4. There is a blockage in the RVOT: the right ventricle is under too much pressure (more than 2/3 of normal or over 80 mm Hg).
5. The person has a heart condition called tricuspid regurgitation (TR), where the blood flows backward instead of forward in the heart because a valve isn’t working properly.
6. A patient has advanced pulmonary stenosis with a high pressure in the right side of the heart (RVSP > 60 mm Hg). Pulmonary stenosis is a condition characterized by a narrowing of the pulmonary valve opening, which can increase the workload on the heart.
Certain groups like the American Heart Association and the American Academy of Pediatrics suggest TPVI for patients with advanced pulmonary regurgitation or pulmonary stenosis. Pulmonary regurgitation is a condition where blood flows back into the heart chamber before it can get out because a valve isn’t closing all the way. These recommendations apply even if the patients do not have symptoms.
The highest level of recommendation is given to patients who have severe symptoms and severe pulmonary regurgitation or pulmonary stenosis.
Groups also consider factors like a patient’s age when they had their first heart surgery, certain heart rhythm data, and the physical effects of having severe pulmonary regurgitation when deciding if TPVI is right for someone. Another factor is measuring how long certain electric signals take to travel through the heart with a test that measures the QRS interval. This can help predict future heart rhythm problems and risk of sudden cardiac death.
A thorough check of the RVOT form should be performed as it helps to know if TPVI is doable once the clinical conditions are met.
When a Person Should Avoid Catheter Management Pulmonary Valvular Disorders
A person cannot have a TPVI (transcatheter pulmonary valve implantation), a procedure where a new valve is placed in the heart without open heart surgery, if they have any kind of active infection or if the veins leading into the center of their heart are blocked. These are called absolute contraindications, which means they are definite reasons not to do the procedure.
It’s also important to look closely at a person’s heart structure before planning for TPVI. If they have a heart structure that could cause the squeezing of the blood vessels that supply the heart muscle with blood (coronary compression) when the new valve is put in, TPVI should not be done either. That’s because when the valve expands, it could end up pushing on the blood vessels and blocking blood flow.
Also, if the diameter of the outflow tract of the right ventricle (a tunnel-like part of the heart through which blood leaves the right side of the heart, RVOT) is larger than the largest available replacement valve, TPVI cannot be done safely. This is because the new valve might not fit securely.
If a person has a history of continuous infection of the heart’s inner lining (recurring infective endocarditis) or has a habit of injecting drugs into their veins, these are also seen as high risk factors for getting an infection after the procedure and are often reasons to avoid TPVI.
Equipment used for Catheter Management Pulmonary Valvular Disorders
The balloon-expandable valve was the first heart valve designed to be placed without open heart surgery and is approved for human use. Bonhoeffer and his team were the first to use this valve on humans after initially trying it in animals. Using this valve is less invasive compared to surgery, which makes it a safer option as it has a lower risk of bleeding and infection. It also bypasses the need for a major procedure that temporarily takes over heart and lung functions (cardiopulmonary bypass).
There are currently three types of valves that can be used to fix problems with the part of the heart that leads to the lungs (RVOT dysfunction). However, only two have been approved for use in the US. The first-generation balloon-expandable stented prosthesis comes in two sizes (20 mm and 22 mm), perfectly suited for RVOT dimensions that range from 16 mm to 24 mm. This device is essentially a stent, or wire mesh tube, with an incorporated valve that’s made from a piece of cow’s jugular vein. When fully closed, this stent is 34 mm long but it shortens to 28 mm and 24 mm when expanded to 18 mm and 22 mm, respectively. Most commonly used is the balloon-expandable valve, since it was the first one commercially available of its kind.
A new innovative approach was developed for patients with a large RVOT diameter (the part of the heart that pumps blood to the lungs) but with suitable branch pulmonary artery diameters. This approach uses dual valve implantation in those branches, although it is less common.
The second-generation balloon-expandable valve came on the scene in 2016. It’s now being used for aortic valve interventions and was also approved for use in the pulmonary (lung) area. With a size range (20 mm, 23 mm, 26 mm, and 29 mm) wider than its predecessor, this valve is suitable for placement in conduits or large RVOTs (greater than 22 mm). The valve is crafted from bovine pericardial (heart sac) tissue and sown onto a rigid metal frame made from chromium-cobalt, allowing insertion of larger diameter valves into large conduits and native RVOTs. The valve size after implantation varies between 14.3 mm and 19.1 mm depending on whether a 23 mm or 29 mm valve is used. This second-generation valve may offer some advantages such as its compatibility with smaller sheaths and broader diameter options, increasing the number of potential candidates for the procedure. Durable frame design possibly lowers the risk of fractures.
Not approved yet for lung use is the third-generation balloon-expandable valve, currently undergoing clinical trials in the US. It’s designed with a special cuff that seals around it to prevent leaks.
In addition to the valve, other tools used for the procedure include stiff wires for additional support, standard pigtail catheters for optimal visualization, and medium or high-pressure balloons to measure RVOT size. Large sheaths cover conduits and help guide other instruments to the RVOT. Occasionally used are covered stents which provide a place to set the artificial valve and lessen the risk of damage if significant dilation is needed for severe narrowing of the RVOT. Vascular closure devices are typically used before inserting large sheaths to maintain control over bleeding after the procedure.
Who is needed to perform Catheter Management Pulmonary Valvular Disorders?
When it comes to really complex heart procedures, a team of heart doctors are the key players in making sure everything goes well. This team includes specialists like interventional heart doctors, heart surgeons, other heart doctors who don’t do operations, and doctors who handle anesthesia during heart procedures. These professionals should have past experience in handling similar complex heart procedures.
It’s also important to have facilities for a special life-support procedure (called ECMO) ready, in case the patient’s condition becomes unstable during the procedure. However, the need for this ECMO support during the operation is usually very rare.
Doctors who specialize in heart care for children or interventional heart procedures and who are skilled in imaging technologies like a cardiac magnetic resonance imaging (CMR) and echocardiography, are great assets in assessing and planning the procedure. Nurses play a crucial role in looking after the patient before and after the procedure. They monitor important health signs, do necessary lab tests, confirm the patient’s blood type, check kidney function, and ensure the patient stays well-hydrated.
Nurses who specialize in heart procedures have the vital job of making sure blood is available if needed, especially in case of any possible bleeding events during the procedure. After the operation, they need to closely monitor the site where the procedure was done and watch the patient for any possible complications.
Preparing for Catheter Management Pulmonary Valvular Disorders
When a patient needs a procedure for their heart, doctors perform a detailed check of their medical history. It’s crucial they understand how the heart is shaped and take note of any previous surgery details, such as changes made to the right ventricular outflow tract (RVOT), which is a part of the heart that helps pump blood to the lungs. They may also need to understand specifics about issues faced during previous operations.
To gather exact details, doctors rely on several tests. These may involve previous evaluations of heart pressure (hemodynamic evaluation), heart monitoring tests (EKGs), stress tests, or imaging techniques like cardiac magnetic resonance imaging (CMR) or computed tomography (CT) scans. Important details about the heart’s functioning and structure, such as functioning of both ventricles, the shape of RVOT, narrowing or leakage of the RVOT, and tricuspid regurgitation (TR), a condition where the valve between two chambers in the right side of your heart doesn’t close properly, will be taken into account. They also keep track of the patient’s veins to ensure a smooth path for delivering treatment.
The ideal treatment approach can depend on several factors including the shape of the RVOT, how flexible and stretchable the RVOT is, and the layout of the coronary arteries, which supply blood to your heart. CT or MRI scans can help doctors get a thorough image of the RVOT, and identify any blockages. If the RVOT is shaped like a pyramid, narrower in one end and wider in the other then treating it with a small tube to support the blood flow (transcatheter intervention) can be challenging. On the other hand, if the patient already has a structure to help blood flow (homograft or conduit) in place, then the process is typically more straightforward.
Doctors will also consider how flexible and stretchable the RVOT is as another key factor for treatment. CMR imaging can help doctors find out the stretchiness of the blood vessel, which cannot be detected by a CT scan. A balloon testing can assist doctors in evaluating how well the RVOT expands. Currently, TPVI, a procedure to improve the blood flow from the heart to the lungs, can be used even if the patient’s RVOT is unmodified, as this has been proven to be safe and effective for the same group of patients.
How is Catheter Management Pulmonary Valvular Disorders performed
When replacing a patient’s heart valve with a new one, anesthesia or deep sedation are typically used, with a surgical team on standby. There are various points for accessing the vein, such as through the leg, neck, or under the collarbone. The femoral approach (through the leg) is generally the most commonly used. However, neck access provides a better angle for certain patients, and may be used for smaller patients whose veins are too small for the femoral approach.
To prevent blood clots, a medication called heparin is given to the patient to prevent the blood from clotting too quickly. Antibiotics are also given to prevent infections due to any introduced stents or hardware. A right heart catheterization is done, which means a tube is inserted into the heart to measure pressures.
The tube traverses the largest opening of the tricuspid valve (a valve within the heart) with the help of an inflated balloon. This helps to avoid any small spaces within the tricuspid valve or RV trabeculations (small muscle bands within the heart) that could make it hard to pass larger tubes and risks damaging the tricuspid.
Images are usually taken of the pulmonary artery and RV for various views of the heart. The AP projection or an “X-ray-like” image of the RVOT, a part of the heart that has been expanded using medical devices, can be helpful in determining the conduit’s shape, length, and diameter. Knowledge of the location of the large blood vessels close to the heart (coronaries) can help predict how the conduit will respond to being tested by the balloon.
Knowing when to intervene or when to make a treatment change is crucial. This often requires expanding the RVOT or conduit and potentially “pre-stenting” of the conduit. Pre-stenting means inserting a stent (a small mesh tube) into the blood vessel to keep the blood flowing smoothly. This is especially useful for patients with serious narrowing of the conduit. It also provides a clear and easy to spot target area for placing the valve later.
There are several key steps to prevent serious complications before implanting the stent. In severe cases, it’s important to slowly and gradually expand the conduit, usually in 2 mm increments. This helps to lower the risk of tearing and lets any tears that occur be fixed quickly.
To prevent the potential for coronary artery compression (a dangerous situation where there is decreased blood flow to the heart), it’s important to check the coronary artery anatomy, especially in patients with complex congenital heart disease (CHD). If coronary artery compression is detected, the procedure is generally not possible. It is also crucial to check for compression of the aortic root, which can lead to a leaking aortic valve.
Once ensuring that the conduit can be safely expanded and there’s no risk of coronary compression, the next step is “pre-stenting.” This often requires using bare-metal stents – metal tubes placed into the artery or vein and left there permanently to hold the vessel open.
Picking the right size and type of the pulmonary valve for implantation is crucial. For example, the first-generation transcatheter valve system allows for new valves ranging from 16 mm to 22 mm in diameter. These new advancements allow for a safer and more effective procedure overall.
Possible Complications of Catheter Management Pulmonary Valvular Disorders
Although it’s rare, a person with very weak heart function might experience several problems during a procedure. They may have problems with their heart valves, blood pressure dropping, and unstable heartbeat due to the mix of a heart condition and stiff wire used in surgery. More serious issues can include the valve shifting into the pulmonary artery, blocking blood flow, compressing the coronary arteries, or the rupture of the graft causing severe bleeding. Luckily, these are rare occurrences. Severe graft calcification and the use of a homograft have been identified as risk factors for rupture. In cases of rupture, most can be managed with a stent that covers the rupture, but sometimes, surgical replacement might be necessary.
Another serious but rare complication could be the movement or displacement of the valve, which might then need to be surgically corrected. If the valve moves to another pulmonary artery, this can be handled by deploying another valve. Another proposed solution involves putting the dislodged valve into a large vein named the Inferior Vena Cava and then opening the valve leaflets with stenting. However, this does carry certain risks such as injury to the heart valve, heart, and vein.
In the long term, the risk of a stent fracture which is the most common reason for re-intervention with the first generation valve remains, pre-stenting, the patient’s age, high heart valve gradient, a smaller conduit diameter, position of the valve, stent recoil or compression after deployment are risk factors. Various types of fractures range from the least severe, where there’s a disruption without loss of stent integrity, to more severe forms where the stent breaks apart. The most severe types of fractures may need surgical replacement or a repeat of the procedure.
More recently, heart valve infection has been highlighted as a significant risk, appearing in about 2.4% of patients per year. Risk factors are being male, having multiple stents, undergoing unprotected dental treatment, a previous history of endocarditis (heart valve infection), and non-compliance with aspirin. This type of infection can be identified by evidence of valve dysfunction along with bloodstream infections. A range of organisms can cause this infection, with Streptococcus viridans and Staphylococcus aureus being the most common. Sometimes such infections can be medically treated and cleared. However, if the valve doesn’t function properly after infection, patients might still need to replace the valve surgically, even if the bloodstream infection can be cleared.
What Else Should I Know About Catheter Management Pulmonary Valvular Disorders?
Transcatheter Pulmonary Valve Implantation (TPVI), a non-surgical treatment for right ventricular outflow tract (RVOT) dysfunction, is recognized as a safe and effective method ten years after its approval in the United States. In this treatment, the valve in the heart that helps control the flow of blood to the lungs is replaced. Mainly, this approach often leads to less pressure on the blood flow, minor insufficiency, with a reasonable rate of complications between 6% and 13%.
Through various studies, the process has also proved its clinical effectiveness, with prominence being placed on its ability to lessen the pressure in the right ventricle (the chamber of the heart that pumps blood to the lungs), decrease RVOT gradient (the difference in blood pressure between the right ventricle and the pulmonary artery), and mitigate pulmonary regurgitation (backward flow of blood from the pulmonary artery into the right ventricle).
Other significant benefits include reduction in right ventricle size, increase in stroke volumes (the amount of blood pumped out of the heart in a single beat), and improved New York Heart Association (NYHA) functional classes, which is a way to classify the extent of heart disease. Patients also had improvements in their exercise capacity, and peak oxygen consumption. Additionally, patients had no indications of valve dysfunction or requirement for follow-up intervention in 93.5% of cases after one year.
Repeat interventions with the first-generation valve are very rare. Moreover, most of the patients who received a valve showed survival rates of 98% after 5 years and 97% after 7 years. The second-generation valve also had similar successful results. It efficiently decreases the RVOT gradient, degree of PR, and improves the NYHA functional class along with decreasing RV systolic pressure, RV-PA gradient, and PA systolic pressure.
Second-generation valves also can be implanted in larger conduits – tubes used in heart surgery – and have around a 97% success rate without the need for re-intervention in the following 6 months. So, both the first and second-generation valve systems have shown promising results, especially when the existing conduit is properly prepared with pre-stenting for severe conduit stenosis, which is a narrow or tight spot in the heart.
