Left Ventricular Outflow Obstruction

Podcast Transcript

Announcer:

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

Nicholas G. Smedira, MD, MBA:

Hi, I am Dr. Nicholas Smedira and have been at the Cleveland Clinic for over 25 years. I have performed over 10,000 heart operations. My area of expertise is hypertrophic obstructive cardiomyopathy, performing over 3,000 septal myectomies.

We talk about hypertrophic cardiomyopathy, but the way I think about it from a physiologic point of view is what really matters to the patient is there's something getting in the way of blood getting out of the heart. I mean, it's that simple.

So that's where I talk about, it's actually fortuitous that we stumble upon this one, is understanding the left ventricular outflow tract because that's the problem. There's obstruction in the left ventricular outflow tract, and for decades, everybody thought of hypertrophy. So you had to have hypertrophy, and that was the focus. And I would ask, why are we seeing outflow tract obstruction in patients that don't have any hypertrophy? So how can that be? Because we focus on hypertrophy, and I really started to ask just simple questions is why do they have outflow tract obstruction?

Back then, there was this very simplistic classic view that there was two ways the septum... This is the septum over here. This is the aortic valve. Mitral valve is over here. There's two ways the septum can sort of behave. One is it can be here thick, and the aortic valve is right on top of the septum. Or over here, you see the septum and the aortic valve is here, but it's taken a right-hand turn or turned to the left. So there's an acute angle between the two. This was thought to be seen in older patients. This was your classic hypertrophic cardiomyopathy.

Here's two examples. Here's a young patient who's got this super-duper thick septum. You can imagine if this is the path for blood to get out of their heart, there ain't much of a path right there. And this is the one that would be considered in an old patient where you got a little bit of hypertrophy right underneath the aortic valve, but there's this really acute change in the ability of the blood to get out of the heart. So it comes in through the mitral, gets in here, the left ventricle contracts, starts to push blood. The blood's pushed in this direction and says, "Uh-oh, I got to go around this turn and get out here." The mitral valve comes up and blocks it, and you have obstruction.

So the focus or the physiologic focus in my head was more like, "Okay, this is a left ventricular outflow tract obstruction. This is left ventricular outflow tract obstruction. This is due to super-duper thick hypertrophy. What's going on here? And why do we see this in older folks?" So I started to ask that question.

You also see all sorts of different forms of hypertrophy. Here's this patient has hypertrophy that's not near the aortic valve up here. It's by the apex. You get the thickening, the blood tries to get out, it can't get out of the apex. It gets intense pressure at the apex, and the apex starts to balloon out. You get this apical ballooning, and you can see how thin this has become. It's actually killing the muscle at the apex because it's under such intense high pressure, two, 300 millimeters of mercury, and it starts to die. They get aneurysms. They get thrombus. So that's another variant of it.

The one that I found most interesting was a case like this. If you look at the MRI, there's absolutely no hypertrophy. That's a normal septum, normal being up to 13 millimeters. So 8, 9, 10, 11, 13, maybe 14 is normal thickness, and this patient had severe obstruction with no hypertrophy.

Now the problem is where everything we do is based on DRGs, and there's no DRG that says, "Left ventricular outflow tract obstruction from abnormal mitral valve anatomy and not hypertrophy," because there's nothing there. So it's super confusing to patients. So they meet them, they ask, "Do I have a genetic disorder? Do I have to have my brothers and sisters tested? Are my kids at risk for hypertrophic cardiomyopathy, which is a genetic disorder?” Or do they have just some anatomic variation in their heart that predisposes them to obstruction?

So that's where it becomes extremely complex to figure out, and since we embarked upon this path and the word got out, people have come here because of our interest in figuring out obstruction.

This is what happens to supposedly all of us as we age. As we age, there's this turning of the aorta this way, giving you that right angle, that 90 degrees, for the blood to get out, which is not a great thing for flow characteristics. Similarly, the mitral valve starts to migrate towards the septum as we get older.

Now, I have a couple of theories why this happen. I don't think it happens to all of us, but I think if you have hypertension, the aorta gets a little longer and gets bigger, pushes into the base of the heart. It starts to turn, the septum gets hypertrophied with hypertension. And I think with obesity, where you have truncal obesity, it pushes the diaphragm up, and the apex actually starts to lift up, rather than a twisting here at the base, and then you get obstruction.

Here's a MRI image of this acute angle. You see this turn. This blood would have to go around this little hub, but look at how the aorta is enlarged. As the aorta enlarges radially, that's when we think of aneurysms so that it's getting radially bigger. It also elongates. You can think of anything that's under stretch, starts to stretch in three dimensions, and you start to see this aorta. And in the OR, it has a curve. This curve, it hits the arch vessels here, and it makes the C-shaped curve. You can imagine as this is pushing down into the heart, the heart has nowhere to go. It can't push the diaphragm down, so it turns this way, and I think that's what happens.

This is the thing that started me to think about how this happened. You can look at this X-ray and you say, "What's going on here?" This person has COPD, obviously huge lung virus, and her left diaphragm is elevated. Typically, your right is higher than your left. She had her left lower lobe taken out for lung cancer. When you have that space here, the diaphragm moves up to fill the space. Six months after her lung resection, she develops outflow tract obstruction without any hypertrophy. What happened is, is the diaphragm pushes the tip of her heart up towards her shoulder, that abnormal flow pattern, and she gets outflow tract obstruction with zero hypertrophy.

So that makes me think or made me think that if anything pushes our diaphragms up, and a lot of people with severe truncal obesity, I think that happens, and you get a little hypertrophy from hypertension, the next thing you know you're predisposed to outflow tract obstruction, and you don't necessarily have hypertrophic cardiomyopathy.

So we did a study, we looked at this angle after I thought about it, and we found that this angle between the apex and the aorta is the most important and powerful predictor of obstruction, much more so than septal thickness. So it seems to be a real phenomena. Now, people are writing papers about that.

We also see that the mitral valve leaflet in patients that have hypertrophic cardiomyopathy, so these are patients that have the thickness, their mitral valve is longer than should be for somebody their size. But what happens is, is if you do this with your earlobe, the skin will stretch. And when you have obstruction, you have something pulling your mitral valve to go towards the septum. When I look in there, it actually looks like somebody's been stretching it every time the heart beat. So it looks like it's been stretched.

So when I talked about this paper, it was, is it really, A, you're born with a long leaflet, or is it because it's being pulled 60, 70, 80, 100 times a minute that it stretches out, and it becomes really long? Papillary muscles are important, but let me show you what we do.

So a myectomy is a resection of the septum with the idea that you'll create space between the septum and the mitral valve so that when it squeezes, there's enough space to allow the blood to get out. And if it's due to that angle, you get rid of the bulge so you open it up so it has a straighter shot for the blood to come out.

What I did that's a little different than the standard approach is do a very extensive myectomy. This is the idea behind the mitral valve. This part of the mitral valve lengthens like a tongue under traction being pulled. So the thought is this has to be either folded back under or cut so that it doesn't have a tendency to flip up and block the path of the blood trying to get out of the heart, and there's other abnormalities that you see.

One of the operations that I devised was based on the observation that sometimes the septum is not thick, the valve is not abnormal, but you still have obstruction, and it was my observation that the papillary muscles itself could be the problem. That they were too mobile, they were too floppy, and that under vigorous exercise, they would go back this way, and then snap back up towards the septum and allow the leaflets to come up and block the blood getting out. So I figured out a way to use pledgeted mattress sutures to pull everything back towards the back wall to prevent obstruction.

Now, it was a real interesting case. It talks a bit about surgical innovation. It was a young kid. He was 17 years old, and he had a seizure disorder since he was a little kid. So it looked like he was having more of these things called absense seizures where you kind of just fade out for a second.

They brought them in into our seizure monitoring unit, had him run around and he'd had these events, but he wasn't having any seizures. We couldn't figure it out.

So we brought him to our exercise lab, had him run on a bicycle. Because he was so fit that if we ran him on a treadmill and we got him off the treadmill and put him on the table, and then you did the echocardiogram... That's how we do an exercise stress test. They put it at like 10 degrees incline and have you run as hard as you can and put you down. His heart rate would recover so quickly we didn't see the obstruction. So we had him sit on a bicycle and pedal as hard as he could. And while he was pedaling, we did the echo, and he had obstruction, but he had no hypertrophy.

So here you got a kid who’s 17, 18, he's got a seizure disorder. The last thing you want to do is put a mechanical valve in him, put him on Coumadin and have him have to manage Coumadin and an INR and a bunch of anti-seizure meds, which as you know, interact with the metabolism of Coumadin. It's a whole mess.

So I went in and I did this operation in a different way to try and pull those valves back, and it worked. We came off the heart-lung machine, looked, and it was like, "Wow, this really works."

So that's some of the things that we've learned. You have a choice. You can take muscle out and that opens up the outflow track. Or you can take the mitral valve out and put in a valve, and that gets rid of the anterior leaflet moving towards the septum, which is called SAM, and that relieves outflow tract obstruction. Then you can do everything you can think of in between to do it. The goal is create space and keep the mitral valve leaflet from coming towards the septum.

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