Diagnosis & Surgical Treatment of Aortic Dissection

Podcast Transcript

Announcer:

Welcome to Cleveland Clinic Cardiac Consult, brought to you by the Sydell and Arnold Miller Family Heart, Vascular & Thoracic Institute at Cleveland Clinic.

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. Most people present with pain, chest, back, abdominal pain. It's usually sudden in onset. You hear that classic tearing sensation. The people know what's going on right when it happens. They can present in shock, passing out, stroke, can't move their leg, their kidneys may be failing. All these things really kind of come back to blood flow not getting the where it's supposed to go.

You see the ones over here was an angiogram. We almost never diagnose it with that anymore. We see that this is the most common modality here is the CAT scan. CT is the best. TEE is pretty good. It's invasive. You've got to get someone to put a TEE probe down. MRI is good, but getting into an MRI acutely, a lot of times, is very hard to do. It's a long test as well. And an angiography, you can diagnose it with it, but it's less readily available as well.

Gating. You guys may have seen that term on CAT scans, gating and not gating. All gating means is that they time the pictures of the CAT scan to the heartbeat. The ascending aorta is close enough to the heart that if you don't time it to the heartbeat you get movement. You can imagine when you're taking a photo and someone's running, it's blurry. It's hard to draw the outlines of things for that. Whereas if they time each picture that the CAT scan takes with the same spot in the heartbeat, you eliminate that movement of the heart. This is the same patient. On the left they didn't gate it, so they called it type A dissection there. It looked like there was a flap. But really, if you timed it to the heartbeat with a gated scan on the right there, you can see that that actually was just a wall of the aorta and it was motion artifacts. So that's what gating means if you hear people talking about getting a gated CAT scan.

You want to include the abdomen and pelvis because a lot of times these track that way. The echo is good to know before surgery just to find out if the heart function is affected, if the valves are affected. In redos, we think they're a little bit more stable because there's scar tissue containing everything. They're also harder to get back in emergently, so oftentimes we'll get a left heart catheterization because there's time to do that in a redo situation.

If you get to the hospital, we'll start you on blood pressure control and heart rate control. So beta blockade is what they call impulse control. Basically decreases the stress on the wall of aorta because your blood pressure will be blunted as it goes from diastole to systole. It decreases the rise of the rate of that blood pressure to protect the wall, and then also we want to keep blood pressure down. This whole thing is the ascending.

The basic goals are you cut out the main entry tear in the ascending aorta, establish predominantly true lumen flow. Sometimes, like I said, you get flow into the false lumen and beyond in your repair if the dissection goes the whole way. But if you reestablish it where the bulk of the cardiac output goes in the true, it usually supports the true and keeps it open. You want a functioning valve, you want coronaries that work, and you want to put the layers back together. That's the minimum strategy. So what they're showing there is a hemiarch if you ever wondered, or an ascending replacement, the root's unreplaced and the arch is unreplaced.

So cannulation is how we hook you to the heart lung machine, putting the aorta back together. If you're taking care of a patient and they have an incision off to the side, that's the axillary. It's a good spot. It's not the aorta so it's usually not affected. It's not torn. It can give you good blood flow to the brain so it can help people who maybe have compromised blood flow to the head. This is why, if you have a patient with an axillary cut down for cannulation, you want to make sure you get good neuro-effects to that right arm. There is a nerve right there. It's big. We see it and push it out of the way, but it can get irritated just by that, having the inflammation of an incision there. It's a good vessel. It's usually not diseased with atherosclerosis, plus you protect the brain, but it takes a little longer.

Femoral artery is becoming less and less favorable. It's quick. We can get to the femoral artery quickly, but a lot of times it's diseased in people who have atherosclerosis and it can increase the malperfusion up flowing backwards sometimes and make the dissection worse. You usually shouldn't cross-clamp the aorta, put a clamp on the ascending, because it can even further increase false lumen and cause a rupture. But it's quick.

This is becoming more popular as we're getting better TEE experience and working together with anesthesia. Basically, you stick the ascending aorta with the needle and you get it into the true lumen and feed a wire through so that they can see on the TEE probe, the echo, and then feed in the cannula with the wire. But it's a little more nuanced. It's quick, but you have to be skilled in it. You have to have a good echo. You can cause more malperfusion if you do it wrong or you can cause a rupture.

We cool people down when we do these surgeries because we stop blood flow through the aorta to do that distal repair, so they call that circulatory arrest. Here most of us don't use straight circulatory arrest to cool people down, but we'll usually give some blood flow to the brain still. That's called neuroprotection or neurocerebral protection. You can run it backwards up through the veins. It's called retrograde. So basically we snare the SVC, the superior vena cava, and run blood flow backwards, upwards, during the circ arrest time and it cools the head, it flushes out any air or debris, but it's a little less physiologic. You can imagine that's not the way blood normally flows.

The other way is antegrade, so that's where you run blood flow up the brain through the innominate and the carotid arteries. That's more physiologic, but sometimes it's a little more cumbersome with a setup, especially if the vessels are fragile. If you have that axillary it facilitates it because you just clamp the innominate artery where it joins and then goes up the back.

You've got to protect the heart. So we give a cardioplegia. That's the medicine and blood mixture we give the heart to stop it in every case. A lot of times I'll start with a dose of going backwards through the heart, we do that often, and then get the aorta open and give some from the coronaries directly if they're not too fragile. If the heart starts to distend while you're cooling down and it fibrillates, it can start to distend if you have a really leaky aortic valve, which is bad for the heart. So sometimes we'll put a vent in and decompress the heart.

If you hear these things called elephant trunks and frozen elephant trunks, those are basically grafts, so stents or cloth tubes, that hang down into the descending aorta inside of the aorta, like an elephant's trunk would hang down. A traditional elephant trunk was just the same material as an ascending replacement, a cloth tube, a Dacron tube, and you would just stuff it inside and you can use it later, then, if you had to fix the descending. When they invented stents and started incorporating those, they called those frozen. They're more rigid and you put them in when you're under circulatory arrest, those are frozen. But anyway, they're both graft material, either stents or cloth, that hangs down in the descending aorta that you can use in a later repair if you needed to extend it with a stent or to do an open descending.

This is how we put the layers back together. You can use fowl. I like to use strips of pericardium, bovine pericardium, or a combination of it. Basically just sandwich the layers back together and try and reestablish all the blood flow into the true channel and seal off the main entry tear in the false.

You can get some chronic ones later on. So here's somebody that had a type A repair before and they had maybe an arch that grew into an aneurysm. You're looking down the arch right there. So here's the head vessels going up this way. Here's the old cloth tube, and you can see the stitching right there. See these big holes or tears? Those are distal anastomotic new entry tears, or DANEs. So you're sewing wet tissue paper together, that's kind of the consistency, so you can imagine some of these stitches pull through. So it's not bleeding, but it tears that flap and it doesn't seal off, so you get some continued blood flow oftentimes. This probably happens on most hemiarch-type repairs. Not all of them. Certainly you can get a perfect repair, but a lot of times it's just so fragile we'll get some of those. As long as the bulk of the blood goes down to true lumen, though, a lot of times these can be managed chronically.

Here's some of the extended arch repairs you guys may see. The one in the middle is the one that Dr. Roselli champions here, and we use a lot, B-SAFER, which is an acronym that stands for branch stented anastomotic frozen elephant trunk repair. We place the stent down, you cover the origin of one vessel, usually a subclavian, and then you cut a hole sometimes in the stent and put a side stent into it so you don't have to debranch it. The other ones can be debranched or maintained as an island. If you hear us dropping off a patient in the ICU and we say, "B-SAFER," this is what we mean. But it's an extended arch repair.

Well, thanks for having me. It was great talking to you. If you have any questions, don't hesitate to reach out.

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