Mark Slaughter, professor and chair of the Department of Cardiovascular and Thoracic Surgery at the University of Louisville and cardiovascular surgeon with UofL Health, talks about a new solution for heart failure.
Interview conducted by Ivanhoe Broadcast News in October 2021.
Is your specific area of interest cardiac surgery?
DR SLAUGHTER: My area of expertise would be in surgical treatment of heart failure and the development of mechanical solutions for cardiovascular disease.
Heart disease and heart failure is a huge burden in the United States. Could you give our viewers some perspective? How serious is this and serious to the point where a transplant is needed?
DR SLAUGHTER: Heart failure in the United States has become a huge problem. There are approximately six million patients that have the diagnosis of heart failure. There are approximately two hundred and fifty thousand deaths per year. A lot of it is a result of the improvements in surviving heart attacks, angioplasty, stents. Many, many years ago, a lot of these people would have died and not survived. And our cardiologists are now able to save them and for many years [they]will lead productive lives. But ultimately, due to the damage that was done, many of them will progress to have a very weak heart, their heart dilates, and they develop heart failure. Historically, transplant was really the only option for these patients. Overall, the total number of transplants really has not changed in the last 20-plus years. Itvaries somewhere between two thousand to two thousand five hundred. Certainly, overall, the results have improved some. But in general, there’s just a persistent donor shortage. So, for decades now, we’ve been looking for a mechanical solution. It sort of would make sense that if we can build a rocket and send somebody to the Moon, you think we then would be able to develop a pump that would be able to do things similar to the heart. It turns out, though, that doing that is probably as difficult as going to the Moon because the heart has multiple different types of muscle fibers, the electrical conduction system, things like that. There have been tremendous advances. And we’re very excited about the most recent one and that is the Aeson total artificial heart that’s been developed by Carmat.
Can you tell me a little bit about the Aeson and what makes this different than some of the other artificial hearts and pumps that have been used?
DR SLAUGHTER: I think it’s worthwhile just quickly to mention. In the ’60s and ’70s, the original intent was to develop a total artificial heart that would serve as a replacement or an alternative to heart transplantation. Along the way, several were developed… the SynCardia or what was called the Jarvik total artificial heart at the time and subsequently the AbioCor total artificial heart. Actually, Penn State had a total artificial heart. But as one could imagine, with your original sort of devices, you learned a lot. There were some issues. And along the way, it became apparent that many of these patients actually could survive with just supporting the left side or what then became known as a left ventricular assist device. For several decades, the majority of the efforts then focused on just developing a pump that would do the work of the left side. Tremendous progress was made. The pumps today now are miniaturized. They’re very small. They’ll last 10-plus years and serve a tremendous number of patients. We learned once again along the way, discovered wouldn’t be the right word because it turns out we knew it all along. But there are patients that need support for both sides. It turns out that although the LVAD is successful in many, many patients, there still was a fairly large group of patients needing support for both sides. And it turns out that using those sorts of LVADs on the right side temporarily or work for a short period of time were not a good long-term solution. There are several new total artificial hearts in development. And one of them is the Aeson developed by Carmat. And the advantage is compared to ones in the past is that along the way, once again, we rediscovered compared to the LVADs that we probably do need a pulse. Because with the continuous flow LVADs many of the patients have no pulse or a minimal pulse, meaning if they collapse on the street and you went and checked, you wouldn’t feel a pulse. But they’re alive and doing fine. But it turns out as humans, we probably do need a pulse. They developed a total artificial heart that mimics the human pulse on both the right and left side. Similarly, they have applied what’s called the pericardium or the sac, the lining around the heart, which we know works well for tissue valves and have applied that to the complete lining inside so that it’s now much more biologically sort of safe. It doesn’t form a clot, things like that. It’s much better for patients. Similarly, they’ve improved the motors such that the motors are much more reliable. They’re electrically driven by batteries. The system outside at the moment is much smaller compared to what we had in the past. They really have addressed several issues and that is sort of mimicking the human pulse in both the right and left sides of the heart. It’s much more sort of friendly, biologically compatible with the human body. And just from a reliability and durability point of view, with sort of new sensors and things like that, it’s a tremendous device.
How did you go about implanting the Aeson?
DR SLAUGHTER: It still is a big operation, it’s sort of like standard heart surgery. People think of “open heart surgery.” It does require a certain sternotomy. You have to go on the heart lung machine. In this instance you stop the heart as well. But the reason is because you’re going to take most of it out. You basically have to take out the ventricles, the right and left ventricle, but you do leave the top chambers, what’s called the atrium. So, both the right and left atrium stay intact, as well as what I refer to as sort of like the ring that would hold the valve, the mitral or tricuspid valve. They come out as well, but that tissue is there. So, what you have to do then to reconnect the device very similar to a heart transplant, though, is you have to connect the left side of the heart. We put in sort of like a cuff on the left atrium, one on the right atrium. And it connects to a relatively rigid plate. So that way it won’t collapse, it can’t move. And then the device just slides in. You literally snap it in. And the device itself takes a little bit of time to prepare. But then it has all four of the valves in it already. Let’s just say, as you literally just snap it into place, the valves are already there. Then you just connect what would be the ventricles to the body. The aorta, so the left side that pumps it to the rest of the body. And the right side, the graft goes to pulmonary artery. The idea is that just like in a transplant or in your own heart, the blood comes back to the right side, which we preserve, the atrium, and then it goes right into the device. That device pumps it through the lungs, and then it goes to the left atrium, which we left behind and then goes immediately into the left side of the device, which pumps it to the rest of the body. It takes probably somewhere between four to five hours to implant it. The total operating time is a little bit longer to sort of get going, finish and things like that. I say it’s still a big procedure, but remarkably, because you have patients, you don’t have low blood pressure, low blood flow, you know, other issues. As soon as you reestablish that normal flow, normal blood pressure, a normal pulse, they recover very quickly.
How long are they on the heart lung machine before the Aeson kicks in?
DR SLAUGHTER: It varies a little bit. But the idea is, generally speaking, they’re on bypass about two and a half to three hours.
What are the risks? Is there clotting? Is there a rejection?
DR SLAUGHTER: Surprisingly, it’s really not much different than any other heart surgery. As you mentioned, it’s things that you would think of is obviously it’s a big operation on the heart lung machine. You always worry about bleeding, right, because you’re just throwing everything back into the heart. Certainly, infection whenever you have an operation, routine things like certainly stroke. Once again, nowadays with routine heart surgery and I sort of say routine, you know, air quotes. But people who have bypass, strokes actually are relatively uncommon now. They do occur. But the same way with this device is it’s relatively uncommon. Things that would be specific, though, to the device and you alluded to is in the past that concerns that you would have would be clotting. And that clotting might occur within the device and then that might cause a stroke. With this new biologic lining, so far, it appears to be a minimal problem. You know, never say never. But it appears to be minimal. And then even after surgery, they require minimal anticoagulation. Literally we put them on aspirin and what we call just a subcutaneous heparin injection. They just take a little shot in the fat tissue once a day. They don’t take blood thinning pills.
What does it feel like for the patient? Can the patient feel the heartbeat?
DR SLAUGHTER: Yeah, so that’s really interesting. We’ve done two out of the three here in the United States. One is surprisingly, it’s very quiet because all the other devices in the past were quite noisy. For many patients, that noise actually sort of scared them. Right? Because even when they would try to sleep, they would hear the device. This one, they don’t hear at all. And quite frankly, there’s minimal vibration, minimal movement. So, they really don’t have a sense that they have something in there. Having said that, they immediately feel better because their blood pressure is better. Their pulse is returned to normal. Their breathing is better because their lungs don’t fill up with fluid. To date, actually, I’ve asked both of our patients and they fall asleep without any difficulty because there’s no noise. They don’t feel any vibration. They do notice a little bit of a difference because although the device has pulsations, as you will see, it sort of goes in a container. As well as your own heart would beat faster, you kind of feel that sensation. Some of that is diminished at least in our patients. They don’t notice it.
How long is it designed to be implanted?
DR SLAUGHTER: To get approval, you have to have at least a known durability. So, to date, at least you test it out until about 10 years. But even then, they have what’s called lifetime testing. So there still are devices in what we call sort of a mock loop or a plastic human that are still sitting at the company going every day. And you just let them go on forever until they might fail. But right now, they’re designed to last at least 10 years, which for many of these patients, that would be the equivalent of a heart transplant.
Is it battery operated?
DR SLAUGHTER: Yes.
Does the battery need to be replaced?
DR SLAUGHTER: So generally speaking, they have a bag that has several batteries in it. The batteries themselves will probably last somewhere around six to 10 hours in that ballpark range. So, the idea is at night, though, when someone’s asleep, you don’t want the batteries to run out. You would just plug it in at night. So, you can still roll over, sleep, things like that. When you get up in the morning, then you put in new batteries, unplug, and just, you know, hook yourself up and go. And depending upon what you’re doing, probably sort of later in the day, you might change them one more time during the day. But yes, it’s battery driven, relatively light. So, they don’t really mind having like sort of a large fanny pack, you know, that has sort of a little computer system and a couple of batteries.
What are the implications of having another option, for some of these really sick patients?
DR SLAUGHTER: Yeah, so at least for our two patients, they really didn’t have any other option. And that is, that both sides of their heart were so weak that it resulted in liver and kidney failure. So, they would not have done well with just an LVAD because they had other organ failure, very high blood pressure in their lungs, they weren’t currently a transplant candidate. So, it really was the only option for them to have one operation, where if they recover and do well, they can actually go home. So, we have some temporary things we could put in. But the idea is you can never leave the hospital. For them, they were just super excited. And so, it really is a tremendous opportunity for what is probably going to end up being a relatively large group of patients that would benefit from having the support of both sides of the heart.
The size is smaller, is it better for a woman, or a smaller adult?
DR SLAUGHTER: Yeah. So interestingly, in the past, most of the original devices that were designed, they weren’t necessarily designed to be only for men, but it just turned out based off of size, predominantly only men were large enough that it would fit in where you can close the breastbone back over it. When this device was designed, the idea was for it to potentially fit in more people. In the original European experience so far, though, it had only been men. So that’s why we’re very excited because this essentially was sort of, you know, a normal American-sized woman and it fit without any issues. So, it’s very exciting because to date as many women will die of heart failure as men, but they’ve had fewer opportunities and fewer options. So it really is a tremendous opportunity to sort of equal the playing field for both men and women that have advanced heart failure.
Is there anything I didn’t ask you that you would want to make sure that people know about this?
DR SLAUGHTER: I think it’s important that everyone understands right now that it is still part of a study. And as part of a study, there are things we will discover. I say so far, the patients have all done very well. But as part of a study, we always have to give credit to the patients because we can’t promise them success. We can’t promise them a great outcome. And the fact that they eagerly agree to participate without knowing what the end result would be means they’re the heroes. And I say they deserve a lot of credit for participating and helping us to learn and even help other people in the future.
END OF INTERVIEW
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