Overview of Carotid Artery Stenting
Carotid endarterectomy (CEA) is a traditional treatment method used for severe blockage in the carotid artery. In simpler terms, it’s a surgery that involves making an incision in the neck to expose the carotid artery and then removing the blockage (plaque) usually found in the carotid bulb (a swelling at the base of the carotid artery) and the start of the internal carotid artery.
However, as is the case in many fields of surgery, there has been a shift towards less invasive methods over time. These new techniques involve smaller cuts, less pain after surgery, fewer possible complications from wounds, and a shorter stay in the hospital. One such method is carotid artery stenting (CAS).
CAS is a procedure where a small mesh tube (a stent) is placed in the carotid artery to keep it open, and this can be done through two different approaches. It can either be carried out from the femoral artery (major artery in the thigh) known as a transfemoral approach, or directly through the carotid artery, known as a transcarotid approach. Both these methods are designed to provide an alternative to traditional surgery and intend to reduce potential discomfort and recovery time for patients.
Anatomy and Physiology of Carotid Artery Stenting
The common carotid artery is a major blood vessel that comes from either the aortic arch (on the left side) or the brachiocephalic trunk (on the right side). This artery splits into two branches: the internal and external carotid arteries. The internal carotid artery carries blood to the brain, while the external carotid artery sends blood to the face, scalp, and neck.
Both the internal and external carotid arteries have multiple meeting points, which can aid in maintaining blood flow if either of these arteries gets blocked. This is known as collateral circulation.
The aortic arch, from which the common carotid artery emerges, can vary in its structure. We can classify it into three types for simplicity. Imagine a horizontal line drawn at the top of the aortic arch, and parallel lines where the large blood vessels come off the arch. For a type 1 arch, all major blood vessels start near this horizontal line. If the starting points of the vessels are within the second parallel line, this is considered a type 2 arch. Similarly, a type 3 arch has the starting points located within the third parallel line. The angle of the aortic arch, depending on its type, can have significant implications for certain medical procedures.
Why do People Need Carotid Artery Stenting
Carotid artery stenting (CAS) is a procedure that might be an effective alternative to carotid endarterectomy (CEA) for particular patients who have a severe blockage (more than 70%), and potentially no symptoms in their carotid artery. This procedure is often chosen for people who are at high risk during surgery. This could be because they have severe lung disease, have recently had a heart attack, have unstable chest pain, or have serious heart failure.
Other situations where CAS could be a better choice include individuals with a history of radiation treatment in the neck, which could make traditional surgery difficult; people who have experienced damage to the vocal cords on the opposite side; people with a tracheostomy (an opening in the neck to aid breathing); people who have blockage in the carotid artery on the opposite side; and people who had a previous CEA and the stenosis (narrowing of the artery) has returned.
When a Person Should Avoid Carotid Artery Stenting
There are several circumstances which may prevent a doctor from performing a Carotid Artery Stenting (CAS) through the main artery in the leg. If the person has a very hardened or unique structure of their main heart artery (the aortic arch), a CAS might not be safe. This includes having a lot of calcium buildup in the aortic arch or a particular type of aortic arch, known as type 3.
Additionally, someone who has had a serious allergic reaction to the dye used during this procedure might be at risk. This dye is injected in the body to let doctors see the blood vessels more clearly. However, doctors can give them some medications beforehand to lessen this risk.
In case the doctor plans to perform CAS through the artery in the neck (a transcarotid approach), they might not be able to do so if that artery (the common carotid artery) is less than 5 cm from the collarbone (clavicle). This is because the artery might not be long enough for the procedure.
Equipment used for Carotid Artery Stenting
When performing medical procedures involving blood vessels, doctors need various types of equipment. Some key tools include an ultrasound device, which uses sound waves to create pictures of the inside of your body, and a fluoroscopic imaging system, like a C-arm, which gives real-time X-ray images. Protective measures are important too, like lead shields to protect against X-ray radiation and sterile drapes for cleanliness.
The doctors also use a water-based solution, mixed with a medicine called heparin, that stops blood from clotting too quickly. To make sure the medicine is working, they check how long blood takes to clot using a machine that measures Activated Clotting Time (ACT). The aim is to ensure the clotting time is above 250 seconds to prevent the formation of harmful clots.
Now, depending on the type of procedure – through the femoral artery in the thigh (transfemoral) or through the carotid artery in the neck (transcarotid) – the equipment varies.
For the transfemoral approach, they need a small kit for accessing the femoral artery, various sized wires to navigate the blood vessels, tube-like structures called sheaths to protect the vessels, angle-shaped tubes or catheters, balloon-like devices to open up the arteries if needed, and a device to catch or reverse any clots that may form.
For the transcarotid approach, in addition to the surgical tray and similar tools as above, the doctors need specific clamps to expose the carotid artery at the neck’s base. They also use a small kit to puncture the artery and a system to reverse the blood flow in order to protect the brain against any potential clots.
Who is needed to perform Carotid Artery Stenting?
The surgery generally needs a team of professionals. This includes a specialized doctor known as a proceduralist (like a vascular surgeon). These are doctors with special training in performing procedures on blood vessels. You’ll also see a first assistant. This could be a fellow doctor, a resident doctor (a doctor in training), or a physician assistant (a healthcare professional who works under a doctor’s supervision).
Another important member of the team is an anesthesiologist. They are responsible for providing anesthesia – the medicine that helps you sleep and not feel pain during the surgery. The radiology technician is there to operate machines that help the doctors see inside your body.
Lastly, you will be taken care of by nursing personnel. This includes a scrub nurse technician, who ensures sterility during surgery and hands tools to the doctors, and a circulator nurse, who oversees the procedure and ensures everything runs smoothly.
Preparing for Carotid Artery Stenting
When a doctor performs CAS (carotid artery stenting), they may use different approaches and varying types of anesthesia. Think of anesthesia as a medicine that helps you not feel pain during a medical procedure. They often use the transfemoral approach, meaning they reach your heart through a large artery in your leg, under a local anesthesia, which numbs only a part of your body. Sometimes, they might give you sedation too, which makes you relaxed and sleepy but not unconscious. This approach helps doctors keep an eye on your brain’s activity during the procedure.
Another method they could use is the transcarotid approach, accessing your heart through an artery in your neck, and here they could use local anesthesia with sedation or general anesthesia, which makes you totally unconscious. When using the general anesthesia, your doctor might also use EEG or brain mapping tool to check your brain activity.
No matter which approach is used, it’s very important that your vital signs such as blood pressure and heart rate are closely observed because the procedure can affect these parameters, leading to low blood pressure or slow heart rate. Doctors often have special medications ready to manage these potential changes. Also, they might insert a small tube into an artery (an arterial line) for better control of your body’s vital signs during the procedure.
Before the procedure, you’ll be asked to take certain blood-thinning medications like aspirin and Plavix to prevent any untoward incidence, and you’ll continue these medications even after the procedure.
During the procedure, you will lie on your back and depending on the approach, your neck is turned aside. Sterile methods will be followed throughout the procedure to prevent any possible infection. For both transfemoral and transcarotid approaches, arms can be placed next to your body.
How is Carotid Artery Stenting performed
The transfemoral method involves a procedure where the doctor, under ultrasound guidance, inserts a small tube, or catheter, into the common femoral artery which is a large blood vessel in your thigh. This approach allows the doctor to perform the surgery using the imaging system, but could be constrained by the structure of your aortic arch (the bend between your aorta’s ascending and descending sections) and calcifications (chalky mineral deposits within the arteries).
With a specialized microscopic puncture device, your doctor will guide a wire into your aortic arch. Following this, an imaging test known as a femoral angiogram might be performed to ensure the correct entry point into the artery and assess its suitability for the procedure. The wire is later moved into your aortic arch carefully. A very small tube (catheter) is then maneuvered into your carotid artery (the major artery in the neck) using the wire. Images are taken and checked, and if all is going as planned, a stronger wire is used to guide a special sheath (a tube-like tool) into your carotid artery. To identify any obstructions, multiple scans of the carotid artery will be carried out.
Once any arterial blockages are found, a very thin & flexible wire is used to cross the blockage. A mesh tube (stent) is then inserted to support the artery. If there’s still a considerable blockage even after placing the stent, balloon angioplasty, a procedure that uses a small balloon to compress the blockage against the artery wall, can be carried out to fix this. After the stent has been successfully implanted, your doctor will remove all tubes and devices. Lastly, a closure device will be used to seal off the opening in your common femoral artery.
On the other hand, the transcarotid technique involves the doctor making a surgical cut at the base of your neck where your common carotid artery is located. The doctor uses a duplex ultrasound, which is a type of imaging test that helps visualize the blood flow and the structure of the carotid, to plan the surgical incision. Following this, the doctor will precisely cut through various levels of tissue until the carotid artery is exposed. After accessing this artery directly, an imaging scan is performed. Similar to the transfemoral approach, a flow reversal system, guidewire and stent are also used in this method. If any excess blockage remains after the placement of the stent, balloon angioplasty is performed. The incision in the neck is closed layer by layer, while applying manual pressure to avoid unnecessary bleeding.
Both approaches’ main aim is to restore normal blood flow through your carotid artery and relieving symptoms you might be experiencing. Your doctor will decide which approach is most suitable for you.
Possible Complications of Carotid Artery Stenting
In the transfemoral approach, which is a medical technique conducted through the large artery in your thigh, some complications could happen. These issues might involve bleeding, tearing or splitting of the artery (perforation or dissection), clot formation (thrombosis), or a condition where a clot or other blockage travels to a new area (distal embolization). Complications could also occur during the procedure, regardless of the approach taken. These can include carotid artery dissection or embolization, which involve similar issues happening in the large arteries in your neck.
Sometimes, the stent, which is a small tube inserted into a blocked passageway to keep it open, might not open up as it should, or it could even break. These events could lead to further complications and would require immediate medical attention.
What Else Should I Know About Carotid Artery Stenting?
Various studies have compared two treatments for blocked arteries in the neck, known as Carotid Artery Stenting (CAS) and Carotid Endarterectomy (CEA). These treatments are important to prevent a stroke. In these comparisons, it has been found that the risk of heart muscle damage, or myocardial ischemia, seems to be higher with CEA. On the other hand, the risk of a stroke, also known as a cerebrovascular accident (CVA), seems to be higher with CAS.
Furthermore, the likelihood of the artery becoming narrow again, known as restenosis, seems to be similar with both treatments after two years. Still, CAS appears to have less successful outcomes in patients aged 70 years and over and also in patients with a significant number of white-matter lesions (areas of damage) on brain images.
Therefore, choosing the right patients for CAS is very important. The transcarotid approach of CAS, which involves accessing the artery directly through the neck, may lower the risk of blood clots travelling to the brain, especially in patients with a complex arrangement of the large arteries in the chest (a condition known as a hostile aortic arch).
Currently, doctors are gaining more experience with this technique via ongoing trials. Lastly, the costs of hospital stay and long-term treatment for both CAS and CEA seem to be similar.
