What is an Aortic Dissection?

Podcast Transcript

Announcer:

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Patrick Vargo, MD:

Hello, my name is Patrick Vargo. I'm one of the heart and aorta surgeons here at Cleveland Clinic, and I'm going to be talking about aortic dissection today. Things that we look for preoperatively to try and find people that are prone to have a dissection if they have an aneurysm. So they have a normal aortic valve, but the aorta is 5.5 centimeters, and actually in some more recent guidelines, even five centimeters. And we know those folks are at an increased risk for having a tear or dissection. Bicuspid valves are certainly prone to it, predominantly because they're prone to aortic aneurysm. So about 1/3 to 1/2 of people with bicuspid valve will have some amount of aortic dilation. And certainly the connective tissue disorders, Marfan's, Loeys-Dietz, Ehlers-Danlos, there's a host of other ones too, ACTA2, SMAD3 and we'll continue to learn more of them, genetic mutations that are associated or correlated with dissections.

When you get to around six centimeters, when the ascending aorta is six centimeters, that's where you have the big inflection risk, where you go from a low single digits to almost a 30% risk of an aneurysm dissection that year. So we've tried to head it off ahead of that and run the five to 5.5 range with elective surgery. Sometimes we'll compare the size of the aorta to the height of the person as well. It's a bad analogy, but sort of like shoe size. If you're 6' 4", you're allowed to have bigger feet without it being unusual than if you're 5' 4". So we try to size your aorta to your height. That being said, there is an absolute too big for any height. Just because you're 6' 6" doesn't mean you can have a six-centimeter ascending.

There's a couple classification systems for aortic dissection. Type A is a dissection that involves the ascending aorta. Type B dissection is a dissection in the aorta that does not involve the ascending aorta, so that's the arch and the descending. If you have any involvement of the ascending, it's a type A dissection. Similarly, there's another system called the DeBakey system. So you have one, two, and three, DeBakey one, two, and three. One is a type A dissection, so it involves the ascending, but it goes the length of the aorta. Type two is just the ascending, so it's limited to the ascending aorta. And then type three is your classic descending type B dissection. So those are some of the known, presumably, here when people are talking about them.

The other one that goes along with them is, you might hear IMH or intramural hematoma. It's on the spectrum of dissection. So a dissection is where you actually have an entry tear into the wall of the aorta and a flap gets created that causes two channels of blood flow, one where it's supposed to be, in the lumen of the aorta, and another one when it created a false passage through the wall of it. And if you get a lot of blood flow through the wall of it, it can compromise blood flow or rupture. That's why it's so deadly. And IMH is where you have that blood entry into the wall of the aorta, but it's not free-flowing, it's more of like a bruise. You have just clots at the wall of the aorta and it's not like a flowing channel. So it's on the spectrum of it, but we think of it as a little bit less severe than an outright dissection. Largely treated the same, though, it's an emergency. Sometimes you can watch it a little bit depending on the patient, how risky they are for surgery.

But anyway, when someone shows up to the emergency room with a type A dissection, there's a 1% mortality per hour without surgery. So that's why we rush them off to the operating room if they're going to be a good candidate for surgery. I mentioned how a lot of the aortas dissect when they get bigger. They can dissect at normal size as well. It's definitely a distribution. I've seen aortas grow to 10 centimeters, we operated on one, and it was not dissected. And then there's other ones where they dissect at four centimeters. So it's definitely a range, but we know that inflection point is around five to six centimeters. So the inner layer is peeling away from the outer layer of the aorta wall. And that can cause, if it involves a valve, it can cause acute aortic insufficiency or leakiness, which can cause heart failure. If it affects these coronary arteries, it can cause a heart attack, malperfusion with coronary arteries. You can imagine, if all the layers aren't there, the wall is weakened, so you can actually get a rupture, and you can tamponade from that internal bleeding.

If this same sort of flap is happening up by the head vessels, the ones that go to your brain, then you can end up with stroke, people present with stroke sometimes. And then similarly, if it happens and causes more blood flow in the false lumen and compresses that true lumen as it goes to your rest of your body, you can get ischemia or malperfusion to your viscera, so your intestines, your kidneys, and even your limbs.

The risk factors, connective tissues, aneurysms, the things that we can control a little more, or at least think we can control, are things like high blood pressure, diabetes. Smoking is certainly something we can control as a modifiable risk. We see these with trauma sometimes, so you can have a bad car accident and it can cause an aortic dissection. Things that increase your blood pressure, like cocaine and methamphetamines, can cause dissection. Heavy weight lifting drives blood pressure way high. So there was a study that you hear about sometimes going way back where they put invasive A-lines in athletes and have them lift really heavy things, and while they're lifting up these really heavy weights, their blood pressure goes 200, 300, it shoots way up. So that's why we caution people with aneurysms not to lift heavy things. And then there's other things like inflammation of the aorta, so aortitis. Well, thanks for having me. It was a great talking. If you have any questions, don't hesitate to reach out.

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