Jun 19, 2018
Dr. Pirooz Eghtesady is a pediatric cardiothoracic surgeon at the Washington University School of Medicine in St Louis. His research focus is on congenital heart diseases, with particular emphasis on aortic stenosis and hypoplastic left heart syndrome. In this episode, Dr. Eghtesady discusses the surgical procedure called a Potts shunt as a treatment option for children who suffer from pulmonary hypertension.
My name is Pirooz Eghtesady. I'm here at Washington University in St. Louis or St. Louis Children's Hospital. I've been here for about seven years. Specifically, I'm a pediatric I'm a cardiothoracic surgeon.
My connection to the pulmonary hypertension community stems from the fact that ... I say unfortunately, because that's a reality... I face a lot of the circumstances when children have no other choice, no other option and come to lung transplantation. Kind of correlating to that, was this notion of why aren't we doing the Potts shunt like they were doing in Europe when I first read about it. I was fortunate enough to have supportive partners like Dr. Grady and essentially then it's kind of taken off in that regard. We've seen, similar to the folks in Europe, some dramatic response.
The thought process people have had, which I think is actually on the right track, is that one big distinction in terms of when the onset of right ventricular failure or right heart failure comes about. In patients who have the ability to shunt, to be able to push the blood in the opposite direction, the potential for maintaining heart function for a long duration of time appears to be better than patients who don't have that pop-off, if you will.
When I came here, I started thinking about different ways of trying to improve the outcomes, both as bridging patients to lung transplant, as well as just in general improving the outcomes. First, there was some reticence and some concern about something that you could say it is experimental not having done it before. The very first patient was a very, very sick child that I operated on and was basically on ECMO. It was a patient who had prior surgeries. It was a very complex operation. Fortunately, we got him through the surgery, and he did okay for a while, but it wasn't a longterm solution for him. We then, sort of in that process, we just kept going and we've now done 14 or 15 patients since I started doing those about four years, five years, something along those lines.
It's been known for a long time with any lesion involving the heart that is some kind of obstruction, so whether it's an obstruction at the level of the mitral valve or obstruction of the aortic valve, obstruction of the tricuspid valve, obstruction of the pulmonary valve, those lesions are not well tolerated, because the net effect is that they decrease your cardiac output or they limit your cardiac output.
This is the analogy that I can give you is that the heart is a system and series. Blood comes into the right side, goes to the lungs, comes to the left side and gets out of the heart. Effectively, you've got four valves or four doors along that pathway. Imagine running through a corridor with four doors. Any one of those doors doesn't open properly. The net effect of throughput is limited. If you have a bunch of people trying to get out of a building that's on fire, wherever the door is not opening effectively, you're going to get backup of people and that room, if you will, is going to get really congested. At first, it might be reasonably tolerated, but the more severe it gets and more people get crammed in there, before you know it they're banging the wall, breaking the windows because they need to get out. At some point the damage that comes becomes irreversible.
That is in contrast to when the door is absent or when there is leakage, say, any of those valves. That can be very well tolerated. People can go back and forth. If you have no doors, you can still get traffic. You can get flow. It's just not as effective. When you have bad pulmonary hypertension and blood can't get through the lungs, the consequence is that the right heart starts getting unhappy and starts pushing in to actually the left side, because the right heart and left heart hug each other. If you actually look at it under like sort of a cross section of a heart muscle, the right heart is kind of wrapped around the left heart. The way those two interact with each other is like a dance. When they contract there is, in fact, a specific location where there is three walls, if you will. We talk about the free wall, the LV free wall, the RV and then the intraventricular septum which is the wall in between the right and left. Those interact with each other, and when the right side gets really pressurized, that septum shifts over and starts pushing into the left side.
It has two consequences. One, is the fact that the right side is struggling, but it also starts impacting the left side, so your net effective cardiac output goes down even more, more so than you would expect simply because blood is not getting around. The ventricle, it can build up muscle, but after a time, what happens when the stress is extreme, the muscle gets replaced with scar tissue. At that point, when you start getting scar tissue, you can't really reverse it, whether it's on the right side or it's left side. Currently, there really isn't a great way.
If people had a massive heart attack, historically, the reason heart attacks were so deadly was because by the time people would get blood reperfusing the heart muscle to salvage it, it would take so long. So much of the muscle would die and get replaced by scar tissue that you would be crippled from heart failure even though things had been fixed, if you will, by restoring blood flow. Now, because treatment is more aggressive and people get to it faster, in fact, they struggle to have trials to show efficacy of various treatments because you don't end up in that situation. We have so much of the heart muscle replaced by scar.
Intervening at any point prior to development of that scar tissue is really important. Our ability to assess the amount of scar tissue is very limited. The ways that we can do that are some of them are indirect using echo and catheterization, but they're not super precise. With MRI, if it's really bad, you can tell. Again, you really can't assess when it's in the early phases of it. It makes it tough.
The notion of being able to protect the heart, protecting the right ventricle, and the ways that we do it is by looking at echo and by looking at MRI to make functional measurements. It really is the only way we can do it, and we try to protect the right side, the right ventricle. The concept of the Potts shunt is before you've sort of fallen off that curve, before that process has happened, you create a pop-off for the right ventricle so it doesn't have to push as hard at the expense of having some of blood bypassing the lungs, so it doesn't get oxygen, but it allows the heart to work more effectively. You improve the overall cardiac output of the patient, so the ventricular septum no longer shifts as much so the overall effective heart output, the cardiac output improves.
Most of the patients who have been here, been here typically for about two to three weeks, somewhere in that range. Particularly when you go through a thoracotomy, it's a painful procedure in that regard and does take some time for rehabilitation. Generally, the patients have spent about five days in the ICU. It kind of depends on the condition of the patient, so the patients that are coming in who are ... and I know this sounds like an oxymoron, but patients who are in good shape, they do really well. If they're very sick coming in, then I think that translates into the outcome. We had one patient who had gone to the catheterization lab and ended up on ECMO, and they had sent the patient to us on support, and that patient never left the ICU. It really depends on the situation of what the patient's condition is coming into the operation. On average, I would say most patients are in the hospital for about somewhere around two to three weeks of which maybe a week of that is in the ICU and the rest of it is kind of rehabilitating, walking around, things like that.
Please discuss it with your physician, with your pulmonary hypertension physician. It's my general impression. This is not specifically for this procedure, but in general, that a lot of times we wait until the very end. You cannot expect good results when you have waited too long. My overall impression even with this relatively limited experience that the younger the patients and the better condition they are, the better the outcome to the point that some I've seen them be able to completely come off of therapies.
It's one of those things that just being aware, gathering as much information about it. It's a very personal decision. The family has to sort of weight the risks, benefits. If they're plugged in with their pulmonary hypertension colleagues, physician colleagues that are providing guidance and are familiar with the procedure, that's great. If not, they can always reach out. There's a number of people now that are developing expertise beyond even the surgical aspects of this.
Dr. Dunbar Ivy in Colorado, we work with him very closely. We've had a number of his patients come through. He has a fair amount of experience about those patients and how they do. I think connecting with physicians like him, Dr. Grady and various folks, I think it can be an opportunity to learn more about the procedure. Certainly, I'd be happy to talk to any family member who is interested or wants to have more information about the procedure and the details of it. I think that is what I would want them to know most, that it's available. The results are promising and sooner than later is the key. That's what I would say.
My name is Pirooz Eghtesady, and I'm aware that I'm rare.
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