Overview of Catheter Management of Coarctation
Coarctation of the aorta is a type of heart defect that someone is born with. This condition is fairly common among heart defects, with around 3 out of every 10,000 babies born with it. The defect involves a narrowing in the main blood vessel of the body (the aorta) which reduces the flow of blood from the heart to the body. Usually, the narrowing is at a specific point near a blood vessel called the ductus arteriosus. This condition can vary, showing up at any age, being linked with other heart problems and presenting different symptoms.
Coarctation of the aorta was first recognized as a medical condition back in 1760. Without treatment, it tends to worsen over time and could lead to early death. An autopsy study showed that on average people with this condition died at age 34 and 75% of them died by the median age of 46.
The first surgery for coarctation of the aorta was performed in 1944. The procedure involved cutting out the narrowed part of the aorta and joining the ends back together. However, this method often led to the aorta narrowing again. This issue led to the development of a new technique where the aorta is cut open at the narrow point and a synthetic patch is stitched over to widen it. This method reduced the chance of the aorta narrowing again but had a high risk of causing aneurysms, which are dangerous bulges in a blood vessel.
A different surgery was introduced which uses a piece of a blood vessel near the heart, called the left subclavian artery. This blood vessel is cut and joined with the aorta where it was narrowed to widen it. This procedure has a 23% chance of the aorta becoming narrow again and could occasionally lead to issues with the left arm during exercise.
Nowadays, the surgical technique of choice for most surgeons involves cutting out the narrow part of the aorta and joining the two ends together. It has a lower chance of the aorta becoming narrow again ranging from 4% to 13%. For adults and those with a longer narrow part of the aorta, a synthetic tube is used to replace the removed portion of the aorta.
Starting in 1982, a non-surgical option became available for treating coarctation of the aorta. It involved using a balloon to widen the aorta. However, compared to surgery, this method had a high chance of the aorta narrowing again over time, especially in newborns. The introduction of stents (small mesh tubes used to hold open blood vessels) improved these outcomes. This article focuses on this non-surgical way of treating coarctation of the aorta.
Anatomy and Physiology of Catheter Management of Coarctation
Coarctation of the aorta refers to a condition where a particular part of the descending aortic arch, a major blood vessel, is noticeably narrowed. This usually happens near the place where the ductus arteriosus (a blood vessel in a baby’s heart) is inserted and just after the left subclavian artery (which carries blood to the left arm) begins. However, this narrowing can also appear in the abdominal aorta or in the transverse portion of the aortic arch.
Interestingly, this area of narrowing can occasionally be part of a larger underdeveloped arch, which is often found alongside other obstructions in the left side of the heart. This can include conditions such as hypoplastic left heart syndrome. It’s also common to find coarctation of the aorta along with other birth defects, such as a hole in the wall separating the two lower chambers of the heart (ventricular septal defect), a two-leaflet aortic valve (bicuspid aortic valve), an open ductus arteriosus (a blood vessel that allows blood to go around the baby’s lungs before birth), and other conditions that obstruct blood flow on the left side of the heart.
The nature of the coarctation plays a big part in deciding whether doctors will treat it with non-surgical methods or need to resort to surgery. Simply put, if the coarctation is native (present at birth), juxtaductal (near where the ductus arteriosus is inserted), or relatively simple and it’s discovered in older children or adults, doctors may prefer a less invasive, non-surgical approach. On the other hand, if the coarctation involves obstructions in the transverse aortic arch, significant twisting or re-coarctation, or abnormal nearby arterial branches, or if there are other birth defects that need correction, surgical treatment will likely be the preferred option.
Why do People Need Catheter Management of Coarctation
The American Heart Association (AHA) heavily advises adults who show significant signs of coarctation or narrowing in the main blood vessel (native aorta) or recurrent narrowing after previous medical treatments to undergo a procedure known as catheter-based stenting. “Significant coarctation” is indicated if there’s an at least 20 mmHg difference in blood pressure between the upper and lower body, or 10 mmHg when the heart’s main pumping chamber (the left ventricular) is not working well, a leakage through the aortic valve (aortic regurgitation), or the blood finding other ways around the narrowed section. To confirm these findings, more advance scans such as a CT scan or MRI of the heart would be necessary.
The clearest need for this procedure is seen in patients with high blood pressure, a pressure difference of 20 mmHg or more between the upper and lower body, and noticeable narrowing as shown by advanced imaging.
Symptoms that indicate a need for the procedure can vary depending on the age of the patient. Older adults commonly have a pressure difference of 20 mmHg or more between the upper and lower body, high blood pressure, and headaches. It is rare, but sometimes they also have troubles with the heart’s pumping chamber (ventricular dysfunction) or high blood pressure when the heart is resting (diastolic hypertension). Typically, children and young adults do not have symptoms but show high blood pressure. Less commonly they also experience headaches.
Besides the need to confirm the coarctation using advanced imaging and understanding the blood pressure difference, the decision between surgical and nonsurgical (transcatheter) treatment relies on other factors; like the age when the narrowing was discovered, whether the narrowing is original or recurring, and the complexity of the narrowing. Unstable infants who are not yet ready for surgery might benefit from non-surgical management as a temporary measure. In younger adults, a preferred approach for both original and repeating coarctation is stent placement.
The recommendation for stent placement is supported by the results from a trial called Coarctation of the Aorta Stent Trial. In the trial involving 105 children, with a median age of 16 years, and adults, the stent placement was successful in 99 percent of participants, and no participants experienced severe events or deaths. Follow up showed that the pressure difference between the upper and lower body remained reduced for two years after the procedure.
Preference for placing a stent relies heavily on the stent’s ability to expand to the size of an adult blood vessel.
When a Person Should Avoid Catheter Management of Coarctation
Doctors often use balloon dilation and angioplasty, which are minimally invasive treatments that involve inflating a tiny balloon inside a blood vessel, to widen it. But they don’t recommend these procedures for babies younger than four months. These methods should also be avoided for patients with a condition called aortic arch hypoplasia, which is when the curve in the main blood vessel supplying the heart is too small. This is because there’s a high tendency for the treated blood vessel to narrow again, and even as soon as 5 to 12 weeks after the initial treatment, more procedures may be needed.
Additionally, when it comes to fixing several congenital heart defects (heart defects present at birth), including coarctation of the aorta (narrowing of the main blood vessel supplying blood to the body), surgery is often a better choice than managing it with a catheter (a long, thin tube).
When it concerns the possibility of injury to the femoral artery (the main artery in the thigh) due to the placement of a large sheath (tube), stenting (placement of a small mesh tube to keep a blood vessel open) is often not recommended for patients who weigh less than 25 kg. Moreover, if a stent is placed in a patient weighing less than 30 kg, the stent will need to be widened multiple times as the patient grows. So, it’s suggested that stents should only be used in patients who can receipt a stent that can be widened to the size needed in adults.
Equipment used for Catheter Management of Coarctation
In treating a condition known as coarctation, there are three common types of devices called stents that doctors use. These are known as closed-cell, open-cell, and hybrid designs. The closed-cell design is made in such a way that it has a more rigid structure because of connected points within the stent material. The open-cell type, on the other hand, has a more flexible design due to the lack of connections in all the parts of the stent. This type of flexibility is helpful when a stent needs to be placed in the transverse aortic arch position, which is a part of your heart.
Hybrid designs have components of both open and closed-cell stents. Another way these stents can differ is how they’re made: some are welded together from single wires, while others are made from a uniform tube that does not have junctions between the components. However, the places where the stents are welded can be points of weakness in its structure. Some newer versions of CP stents have taken this into account by strengthening these welded points with gold soldering.
Stents can also be made of different metals. The most common types include platinum-iridium alloy, chromium-cobalt alloy, and stainless steel. They can be classified as covered and bare stents. Polytetrafluoroethylene (PTFE), which is a type of inorganic compound, is most commonly used as a cover for the stents.
Covered stents are preferred in treating coarctation of the aorta in patients with certain conditions such as genetic aortopathies (a group of disorders affecting the aorta), tortuous aortas (an aorta with many twists and turns), narrow coarcted segments, or aneurysms that may pose an increased risk of complications with the aorta’s wall during treatment. The platinum-iridium stent with an outer cover made of polytetrafluoroethylene is the most commonly used stent in treating coarctation of the aorta, and it’s the only stent to have been approved by the Food and Drug Administration specifically for this type of treatment.
Who is needed to perform Catheter Management of Coarctation?
In less technical terms, treating a heart condition called coarctation of the aorta, which is a narrowing of the large blood vessel that leads from the heart, is a team effort. This team is made up of several medical professionals, each with their own roles and responsibilities. Some team members help correctly diagnose the condition and create detailed images of the affected part of your heart. Imagery specialists then interpret these images.
Others on the team, called echocardiographers, create detailed images of your heart using sound waves. These sound waves allow them to record certain important measurements, which help decide if you need further treatment.
The doctor who plans to perform the non-surgical heart procedure, called an interventional cardiologist, works closely with a heart surgeon. Together, they will determine whether surgery or a non-surgical procedure will give the best result for you. Similarly, doctors called cardiac anesthesiologists are responsible for keeping a close eye on your heart rate and blood pressure during the procedure. They can also do further imaging of your heart if necessary.
Lastly, Registered Cardiovascular Invasive Specialists (RCIS), who are specially trained to monitor your heart function during heart procedures, keep track of your heart’s electrical activity and other important information during the procedure.
Preparing for Catheter Management of Coarctation
Before undergoing a process known as catheterization, which is a procedure to examine the heart, several tests are usually performed. These include a complete blood count (which checks the variety of different cells in the blood), a chest x-ray, and an electrocardiogram (a test that records the electrical activity in your heart). Sometimes, doctors order a stress test to check for any increase in high blood pressure when you’re active and to look for any changes in blood pressure in the arms and legs.
An echocardiogram, a test that uses sound waves to create a picture of the heart, is also often done before this procedure. It helps the doctors determine where the issue in the aorta (main blood vessel in the heart) is, the shape of the aortic arch (curved part of the aorta), and how severe the problem is. The echocardiogram can also check for other heart conditions including ventricular septal defect (a hole in the wall separating the two lower chambers of the heart), a bicuspid aortic valve (a valve with only two flaps instead of three), problems with the mitral valve (regulating blood flow in the left side of your heart), and left ventricular hypoplasia (when the left side of the heart doesn’t develop as it should).
However, echocardiogram may not always provide a full view of the aortic arch, especially in older children and adults. Therefore, other imaging tests like a cardiac MRI or a computed tomography scan (CT scan) of the chest can be used. These advanced imaging techniques can help doctors get a detailed view of the heart issue, know the size of the problem area, and understand the location of structures close to it. This information can help doctors plan the procedure, decide the size of balloons and stents (small tubes used to open up blocked arteries) needed, and identify reference points that can help them during the procedure.
How is Catheter Management of Coarctation performed
Some operations on the heart, including the treatment of coarctation of the aorta, can be performed through a small incision in your body using techniques called balloon angioplasty or stent placement.
Coarctation of the aorta happens when a part of the aorta, the main blood vessel carrying blood from your heart to the rest of your body, becomes narrowly restricted. To treat this condition, doctors usually recommend undergoing general anaesthesia, which is medication that makes you unconscious during an operation. They suggest this because expanding the narrowed part of the aorta might cause some discomfort and you may move around, making the operation more challenging.
The surgeon usually gets to your aorta through a blood vessel in your thigh, known as the femoral artery. The surgeon uses the femoral artery to pass small tubes and other medical tools up to your aorta. They make sure that they’re using the right blood vessel by using a type of X-ray called an angiogram to check that everything is correctly positioned.
In some cases, if they can’t reach the affected segment of the aorta through the femoral artery, the surgeon can access it through a blood vessel in your arm or wrist to guide their medical tools.
In these procedures, the surgeon also usually accesses a large vein in your thigh to perform a complete right heart catheterization, which is a diagnostic procedure to measure how well your heart is functioning. This vein can also be used to place a pacing device, if required, which helps control the rhythm of your heart during the procedure.
After preparing things, the surgeon will administer a medicine called heparin through a vein to prevent the formation of blood clots during the procedure. The surgeon will then start the main procedure with various other medical tools to reach and treat the narrowed part of your aorta.
The surgeon will then measure the affected part precisely to ensure that the medical device used to expand the artery – the stent or balloon – is of the right size and will fit in your unique body contour.
After checking the size using an angiogram, a stiffer wire is used to position a tube, through which the stent or balloon is guided to the affected part of your artery. Once the stent is positioned properly, the surgeon will inflate the balloon to expand the narrowed segment.
A successful operation results in less pressure difference across the stent, improving the flow of blood through your aorta. This procedure should help alleviate any symptoms you may be experiencing due to the coarctation of the aorta.
Possible Complications of Catheter Management of Coarctation
Endovascular stenting is a less invasive way to fix a narrowed aorta, a condition known as coarctation of the aorta. However, it does come with certain risks. The most dangerous of these is the chance of the aorta rupturing, or tearing, which happens in about 1.6% of cases. Some things that increase this risk include the use of a balloon for widening the blood vessel beforehand (known as balloon angioplasty), the coarctation being located in the abdominal aorta, and being over forty years old.
Another possible complication is the development of aneurysms, which are bulges in the blood vessel, after the stent is placed. This happens in about 5 to 9% of cases and is thought to be caused by overstretching the blood vessel during balloon angioplasty and changes in the composition of the blood vessel wall.
Sometimes complications can involve the stent itself, such as it moving from where it was placed (embolization or migration). This tends to occur when a balloon that is either too big or too small has been used. If the stent moves and gets stuck in the aorta or the femoral artery (in the leg), a device called a lasso may be used to retrieve it.
Additionally, the blood vessel can narrow again after treatment in about 13–31% of cases with balloon angioplasty. This rate has been seen to drop to around 2.7% when a stent is used. This may be due to tissue growth inside the stent.
There can also be complications related to accessing the blood vessel through the thigh (femoral access), such as reduced blood flow to the leg and blood pooling under the skin (hematoma). These risks have decreased with the use of special tools for closing the blood vessel after surgery.
What Else Should I Know About Catheter Management of Coarctation?
Fixing a narrow spot in the large body artery (aortic coarctation) through a less invasive procedure (endovascular repair) can play a crucial role in patient’s recovery outcome. It has been found that early treatment, especially in young individuals, can reduce future risk of high blood pressure (hypertension) and increase chances of survival.
While even those treated later in life might experience less survival benefits and a higher chance of developing high blood pressure, the endovascular repair procedure can still prove beneficial. This procedure not only helps in managing blood pressure more effectively but also reduces the need for medication to control hypertension.
Given all the known benefits of repair and advancements in technology that make endovascular repair easier, it has become common to intervene early during childhood. The only drawback of early intervention is that it requires careful monitoring over the years and possibly further treatment in the future.