Mahmoud Malas, MD, MHS, RPVI, FACS, Professor in Residence, Vice Chair of Surgery for Clinical Research, and Chief Division Vascular and Endovascular Surgery at University of California San Diego, Health System, talks about a new approach to treating aneurysms.
What is an aortic aneurysm?
MALAS: The aneurysm is Latin for ballooning, and the aorta is the main vessel that feeds the entire body. It originates in the heart and goes all the way down through the chest and abdomen and branches out into two iliac arteries that end up in each one of the legs. It also branches to every vital organ in the body. So, essentially every important organ in the body is fed by the aorta.
What is an aneurysm then?
MALAS: Basically, you have an aorta where the vessel gets very weak and starts expanding. Rather than be in a uniform shape tube, it becomes like a bulge, and that’s what an aneurysm is – the weakening up of the vessel wall. And, eventually it could rupture. When it ruptures, the patient can exsanguinate very rapidly, and the outcome will be very poor.
What causes an aneurysm?
MALAS: We don’t know exactly what causes it, but there’s a lot of risk factors for it. One is family history. We found in somewhere between 15 to 25% of patients, there is family history where the mom or dad had an aneurysm in the past. We also found a very strong link to smoking. The majority of people who have aneurysms are smokers and have smoked for many years. We also found that smoking increased the rate of growth of aneurysms.
What is the rate of increase?
MALAS: When we find an aneurysm while doing other radiological testing or on physical exams, we typically watch them because the patients don’t have symptoms. In fact, about 80% of patients do not have symptoms. The patient could expand and rupture and not know that they even had an aneurysm. That’s why it’s very important to do screening in higher risk patients. We know that people over the age of 65 who smoke and have family history need to be screened with an ultrasound to rule out aneurysms. The rate of growth is typically slow. A normal aorta in a male is about 2 ½ centimeters, which is about an inch. Once we get to 3 to 3 ½ centimeters, we call it an aneurysm. Aneurysms grow less than half a centimeter a year. Anything that’s faster than that, we’d consider it a rapid growth. If it’s more than 7 to 10 millimeters a year, then that kind of prompts us to fix them. We also know that a certain size, 5 centimeters in a female, which is 2 inches, or 5 1/2 centimeters in a male is when the risk of rupture is higher than the potential harm of the repair and the benefits from a repair exceed the risk of not repairing.
Do most people find out they have an aneurysm when it ruptures?
MALAS: Typically, patients get a little bit of abdominal pain or severe back pain that prompt them to go to the emergency department and this is typically where we find the aneurysm. But, the majority of patients say they get a scan for a kidney stone and incidentally find that they have a large aneurysm.
How would you normally treat an aneurysm?
MALAS: In the past, the only way we were able to treat the aneurysm when they get to the large size that need to be fixed was to do an open repair. This involves significant incision to open the abdomen to fix the aneurysm. We have to clamp the vessels in order to control the bleeding, which in turn add a lot of stress on the heart. Almost 50% of patients who have aneurysms also have coronary artery disease which puts them at risk of having a heart attack from surgery. We will clamp the vessels, open the aneurysm, and then replace it with a tube graft that is made of fabric or plastic. We sew it below the kidney artery or before the vessel bifurcates into the iliac arteries. We have this newer technology called the endovascular aortic aneurysm repair, or EVAR. This is where we actually go through the femoral artery without incision or with a small incision and use wires and catheters to put a stent graft from inside which allows us to fix the aneurysm from the inside.
Can you do that with everyone?
MALAS: That’s a very good question. Patients must have good anatomy to seal that stent graft before and after the aneurysm. We call that the neck of the aneurysm, which we want a healthy segment of the aorta that is not aneurysmal where the stent graft can be fixated, approximately right below the kidney artery. A lot of patients we found, sometimes 20 to 30%, do not have the anatomical criteria to allow them to be a good candidate for EVAR.
What happens to those patients?
MALAS: In the past, we offer them the open repair if they are suitable. But this is a disease of the elderly, so many of the patients are old and have significant heart disease and will not withstand an open operation. When the aneurysm gets closer to the kidney artery or it’s a route involving the vessel that feeds the bowel, we call that pararenal aneurysm or abdominal aortic aneurysm. This aneurysm really cannot be fixed with the standard endovascular repair. So, there’s not much we can offer them.
But now there is something you can offer?
MALAS: We have newer technology that is being studied where we extend the endovascular repair to help treat pararenal and abdominal aortic aneurysms. That involves a fenestrated endograft and branch graft. This stent graft can extend further up, but we cannot lose the kidney artery and mesenteric artery, so we have to have the fenestrations, which are holes in the graft to match the patient’s anatomy for these vessels. Then, we have to extend that with the little stents or with a branch into these vessels so we can keep refusing the kidney, the liver and the bowel.
So, it kind of reinforces those arteries?
MALAS: Yes. It reinforces those arteries and then excludes the aneurysm or depressurizes it. We still have the sack of the aneurysm, but there’s no blood flow and no pressure, so it won’t rupture. We have to seal our repair before and after the aneurysm with this fenestrated technology.
How are you using AI to help you with this?
MALAS: It’s image fusion technology that takes the preoperative patients’ CT scans and creates a 3D modeling that involve over 2 billion different possibilities. It gives us a dynamic overlay during the procedure. When we’re doing the procedure, we take a quick x-ray of the patient. All we need is two vertebral body of their spine, and this technology uses the cloud to fuse those vertebral body with the preoperative imaging. They create that overlay within less than three seconds and we can see where the aneurysm is without using contrast. We can see all these vessels that feed the vital organs. Think of it as a GPS that guides you to navigate through the patient anatomy to get into these vessels and uses the vertebral artery. I always explain to my kids, it’s like when you hold your iPhone, and it uses your facial recognition to recognize you and open up the application on your phone. By taking these vertebral body, it recognizes the patient, and creates the 3D reconstruction.
Explain how it gets smarter as you do more patients?
MALAS: Yes. The difference is, today, it uses artificial intelligence and machine learning. If you think about it, when we do this repair, we have to deliver those big stent graft and use wires, which are rigid. If you take a fusion imaging and you put a wire in, the vessels move. Whatever you created, imaging is not helpful anymore because it doesn’t match the patient anatomy because of the stiff wires. What this technology is doing is using this shift that happened from prior studies to build a prediction model and predict where the aorta is going to move. This is where the machine learning comes in and the artificial intelligent piece of it. As we’re moving the table the patient is on, and as we’re putting different wires in, the anatomy is shifting. We can adjust it also on the table right there to match the patient anatomy.
Can you explain why it is better to use less dye in radiation?
MALAS: So, radiation is harmful. And when you do these cases, they become more complicated with more complicated anatomy. This radiation is harmful to the patient, and it’s also harmful to the team performing the procedure. We all wear lead glasses to protect ourselves, but we cannot put lead on the patient because then we cannot see the anatomy. The second part is the contrast. The newer contrast agents are a lot less toxic, but they still can be harmful to the kidneys. The majority of our patients have some kidney disease and may not even know it. If we give a lot of contrast, we can harm the kidneys and the patient could lose their kidney function. That magnified the more difficult the aneurysm is and the longer the case is going to take, requires more contrast injection. This technology is already helping us use less dye and less radiation.
Interview conducted by Ivanhoe Broadcast News.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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