Created by Vishal Punwani.
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- If a Type B dissection is treated with medication, does this only prevent the dissection from worsening, or can the damaged aortic wall actually heal? (seal over the initial tear and/or the layers that have separated come back together)(4 votes)
- when doing a type a surgery, wouldn't you have to keep it from bleeding? if so, how would the heart still supply the body?(2 votes)
- Q1-yes you have to keep it from bleeding
Q2- there is a machine that takes over the functions of the heart and lungs(1 vote)
- How do you manage an aortic dissection? How do you treat one? Well to remind you, an aortic dissection is when you develop a tear between your intima and your media in your aortic wall. So when you develop a tear, blood will start to get in there and start to tear the layers away from each other. This is a medical emergency and requires immediate treatment at a hospital. And this treatment will depend on whether the patient has a Type A or a Type B tear. Alright, so let's take a close up look at an aortic arch. Type A dissections are unfortunately both the more common and the more dangerous type. So as a reminder, these dissections are ones where you get a tear in the ascending part of the aorta or really any part of the first bit of the aorta before the start of this left subclavian artery here. So a Type A dissection pretty much always have to undergo surgery because for these treatment with just medication has a high rate of mortality. Type B dissections can be managed a bit differently though. So again, to remind you, Type B dissections are when you get a tear between the intima and the media at any point in the aorta, after the left subclavian artery. So these can often be managed medically, which means just with medications and no surgery unless the patient develops complications that require more intervention, like surgery. Alright, so those are the basics. Now let's look at how your specially treat a Type A dissection. So the goal of this surgery for a Type A dissection is really to replace the effected aorta. So let's say that we have our initial entry tear here and we're going to put in the ascending aorta because that's where more of the initial entry tears are. And then through this entry tear, you're going to get blood that gets pumped out of the left ventricle and the blood is then going to track into that initial entry tear, right? It's going to see that tear along the aorta wall and it's going to want to duct inside that tear. And when it ducts inside that tear, it sort of splits the intima and the media away from each other. So every time the heart beats, it'll pump more blood into that tear and that blood will go ahead and split the intima and media further from each other. So when that happens, what you end up with is this flap of intima that has been torn away from the media in the aorta wall. And so right now, I'm going to draw it overlying the blood because the blood is behind it, right? Between the intimal flap and the media. So that's what this is. This is the intimal flap. And let me just highlight this blood even more. I'm going to draw this blood in a bit better. And then on the outside, on the other side of the blood, I'll draw both the media and the adventitia on the other side of the blood here. I'm drawing them both in this light pink color. So what the surgeons will do is they will replace the affected part of the aorta with a graft. So all this aorta which is diseased will get cut out. So just pretend that I'm cutting out the aorta here, cutting out all this bad aorta. So all the layers, not just the intima, but the media and the adventitia as well, all of it gets cut out. And then the part that got cut out gets replaced with a graft. And a graft in this case is a synthetic tube that sort of can take on the role of an aorta. And it looks pretty cool. It looks like this. It's this sort of light colored tube thingy and it's nice and bendy and flexible because if it's going to act like the aorta, it needs to be able to bend and be elastic and withstand pressure. So what happens is the graft is sort of stuck inside the aorta here and that closes up the false lumen. So remember that intimal flap we talked about, that piece of intima that became separated from the media as the blood sort of sheared the two layers apart? Well there's a little bit left over here. So what happens is a graft gets put just a bit further than that intimal flap. And then so this end of the graft gets sutured in. I'll do my stitches in purple. And then this side gets sutured in. And if it needs more reinforcement, then something called a teflon felt will be sutured in around the outside to sandwich this part of the aorta and to keep things nice and stable in this area. So let's do that. Let's actually draw in some teflon felt. So it gets put on the outside and gets put across the end of the graft here. So that helps to keep everything in there nice and stable. So now you've got the graft on the inside of the aorta and then you have this teflon felt on the outside of the aorta. So you can imagine that by doing that, that false lumen is not going to get any more blood in it. And sometimes the surgeons will use a special type of glue called BioGlue and that will help to keep it even more secure. So we'll put some BioGlue on here and it actually sounds like something MacGyver would come up with but it can be pretty helpful depending on the type of dissection that you had. Of course, we have to sew this side up, so we'll use our purple sutures and sew that side up as well. And of course we have to connect this artery back onto the aorta, this major artery that sends blood up to your upper limbs and your head. We'll reattach that to the top of the aortic arch here on our graft and we'll suture that in. And it's probably worth noting that these grafts typically have collagen or gelatin built into them that make them leak proof so that blood can't just seep out of them. So now we've repaired the Type A dissection so now blood can flow normally through the aorta and not get caught up in this intimal media tear here. So that's treating Type A dissections. Let's look at Type B dissection treatments. So people who have Type B dissections are normally treated with conservative therapy. That is to say they don't get more invasive therapies like open surgery like we just saw because the risks of doing the surgery are greater than the risks of managing their dissections with medication. Having said that, there is a minimally invasive surgery that can be done for Type B dissections, and I'll just touch on that before I talk about the medications that are typically used to manage them. So the minimally invasive technique is called the endovasscular stent grafting. And the idea behind this is to take a stent, which is basically just a mesh tube, and it can be made out of fabric or metal, and so you take this mesh tube and put inside the damaged part of the aorta. So it sort of strengthens the weakened or torn wall of the aorta by just being there. I don't know if you did this as a kid, but my brothers and I, around Christmas, we would take those card board tubes that gift wrapping paper came on, so we'd take those tubes and we'd sword fight with them. So inevitably the tubes are swords, they'd become weak, right? They'd become weak because we would hit each other with them. So to reinforce them, we would stick cardboard tubes from toilet paper roles down them and that would reinforce them a bit. So it's a similar idea. So I mentioned that it was minimally invasive, right? Well it's minimally invasive because what happens in this procedure is that your surgeon will take a tube called a catheter and this catheter is holding onto a stent. So it contains one of those mesh tubes. And the catheter gets inserted into your femoral artery. So the surgeon will make a cut right here and thread the catheter in into your artery. And then the catheter will get pushed all the way into your aorta where the defect is. And that is where the stent will get deployed. And when the stent gets deployed, it gives strength to the walls it's covering. It sort of reinforces them. And now that tear can't contribute to anymore damage to your aorta because it's now blocked off by the stent. Alright, so now medications. This is what's referred to as conservative treatment. So if you have a Type B dissection, you'll likely be managed with a few different drugs. And really the bottom line with all these drugs is to get your blood pressure lowered. To lower the risk of further damage being caused to your aorta. So you might be given a bit of a cocktail of sodium nitroprusside, a beta blocker, and sometimes a calcium channel blocker. And again, the goal of these is to lower your blood pressure and to decrease your heart rate and contractility. Nitroprusside is a vasol dilator. So it dilates or opens up your veins and reduces blood pressure that way. A beta blocker refers to a class of drugs that blocks beta receptors of the heart. These beta receptors, when they're stimulated, they make the heart beat faster. So a beta blocker blocks those beta receptors so they can't be activated to make the heart beat faster. Sometimes a patient might be given a calcium channel blocker as well, which can also reduce blood pressure. And it makes sense that these treatments are all focused on reducing blood pressure, right? Considering that a dissection is mainly caused by pathologically high blood pressure, that's really a huge focus in treatment, to be reducing that blood pressure by all means necessary. With either types of treatments, medical or surgical, whether it's a Type A or a Type B dissection, the patient would be put on antihypertensive medications or blood pressure lowering medications for the rest of their life to minimize the chance of another dissection happening. And also to reduce their risk of other hypertension caused problems that may crop up in the future.