Endovascular aneurysm repair (EVAR), or TEVAR (in thoracic aneurysms), is a minimally-invasive procedure that uses stent grafts — small mesh tubes made of metal and covered in special fabric, which are placed inside the part of the aortic wall where the aneurysm is located. The purpose of stent grafts is to exclude the aneurysm from circulation by practically sealing that part of the aortic wall, thereby normalizing blood flow, while also minimizing the risk of further complications, such as an aortic rupture.
How to prepare for this type of surgery?
Despite being safer than classic open surgery, while also shortening the time spent in the hospital, it’s important to mention that not all aneurysms can be treated via EVAR. Certain conditions must be met when assessing if the patient is suitable for this kind of procedure, such as the shape and dimensions of the aneurysm, the presence of blood clots, calcifications, the condition of arteries branching out of the aorta, etc.
This evaluation is done with the help of medical imaging, such as a multi-slice CT scan, which has the possibility to digitally reconstruct the whole vascular system to plan every part of the procedure, including the type of stent graft needed, in advance. In case the CT exam can’t be done for some reason, the aorta may be evaluated using ultrasound.
How is (T)EVAR performed?
Unlike open surgical repair (OSR), patients treated via EVAR don’t need to undergo total anesthesia, which is especially suitable for those who at in high risk for it. Although total anesthesia is still an option, many surgeons choose local anesthesia (which numbs only the area where the small incision is made), with some even preferring regional anesthesia (which numbs a whole part of the body, but doesn’t render you unconscious).
The first step is to make a small incision in the upper thigh area, through which a diagnostic catheter (a tiny tube) is placed and slowly pushed all the way to the aorta. Then, a contrast agent is injected though the catheter to visualize the structure of the aorta and other arteries, thereby confirming what was seen on CT.
This process, called aortography, is monitored under X-ray control, using a method called fluoroscopy. Surgeons can now measure and mark the problematic parts of the aorta, as well as plan the rest of the procedure in detail. Fluoroscopy is also used to control the whole procedure from start to finish.
The balloon with the stent graft is slowly pushed through the catheter and finally positioned. When in the right position, the balloon is inflated, expanding the stent graft until it completely covers the desirable part of the aortic wall from the inside. The balloon is then deflated, and removed along with the guiding wire, and finally, after stopping the bleeding, the incision may be closed.
This process may be slightly altered depending on the location of the aneurysm, which is why different types of stent grafts exist. For example, cylindrical stent grafts are available, which are used in TEVAR as well as in treating higher placed abdominal aortic aneurysms (AAA). But, in AAA where the aneurysm also exists on the iliac arteries, a special, branching, type of stent graft is used. Therefore, repeating this procedure with another stent graft, through an incision in the other thigh, is needed to cover all parts of the vascular system affected by the aneurysm.
What risks and complications does (T)EVAR procedure involve?
After surgery, you may experience minor side effects, such as nausea, fever, lack of appetite, swelling and pain in your legs, or similar inconveniences for a few days.
As in any surgery which deals with major issues, there are, of course, risks for complications such as blood clotting leading to heart attacks and stroke, or kidney failure. Because (T)EVAR involves putting stent grafts inside the lumen of the aorta, it is also possible for the graft to move, or slip after the procedure. Also, keep in mind that the stent graft is, after all, a foreign body, and as such may be susceptible to infection. Therefore, it is important to undergo follow up diagnostics (CT and ultrasound), to guarantee that everything is still in order.
However, the most dangerous complication related to EVAR is the so-called “endoleak”, where the blood leaks outside of the stent graft, slowly filling the aneurysm, therefore additionally expanding it, potentially leading it to rupture. It is for that reason that EVAR procedure is often required to be repeated. This may present a problem due to higher costs of EVAR over open surgical repair, as well as the need to repeatedly expose the patients to ionizing radiation during angiography.