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The innovation of left ventricular assist devices (LVAD) as a treatment option for patients with heart failure had a significant impact in the field. Michael Zhen-Yu Tong, MD, gives a brief history of how LVADs have evolved over the last few decades to be a durable solution for patients with advanced heart failure.

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Evolution of Left Ventricular Assist Devices

Podcast Transcript


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

Michael Zhen-Yu Tong, MD:

Good morning. My name is Michael Tong. I am the Surgical Director of Heart Transplantation and MCS, at the Cleveland Clinic. And today I will be talking about long-term outcomes with durable, mechanical circulatory support. So, long-term support for patients with chronic heart failure is really about mechanical circulatory support with HeartMate 3 and with heart transplantation.

So, the first human heart transplant was done in South Africa, by Christiaan Barnard, this was in 1967. However, most of the research was done in the United States. So, Shumway and Lower did most of the studies and experiments and developed a technique for the heart transplantation. So, the story with Shumway was that, he wanted to be back in academic medicine, he didn't want to go to private practice. So, the only job that he can get at the time was to work the graveyard shift in the dialysis unit. So, that was the only job he can find at the time. So, he took that job, but what that job afforded him was a lot of free time. So, that's when he developed the techniques for transplantation and as we know it today. So, every lemon can be turned into lemonade.

So, what you may have heard about the first heart transplantation in 1967, but what you may not have known was that the first heart transplant at the Cleveland Clinic was just one year after, in 1968. So, what you realize about the Cleveland Clinic that was different was, the emphasis was never on the individual, it was always on the team. And it is that emphasis that still rings true today.

So, the transplants in the first few decades were not all that success. Patients lived for a couple of weeks, sometimes a couple of months, and then they all died because of rejection, they died because of infection. And it wasn't until cyclosporine became available in the late '70s that transplants finally became a viable long-term treatment option. And cyclosporine allowed for us to be able to selectively immune suppress these patients, but not to the degree that they were going to get infections or not to degree where they're going to get bad infections. And it was only until cyclosporine became available that you saw a dramatic increase in the number of heart transplantation in the '80s. And in the '90s, the number of transplantation did drop in the United States and around the world, but in recent years, it has come up. The reason it dropped into 1990s was, a lot of the donors at the time were from homicides and from crimes. And that dropped in the United States quite a bit by half in the 1990s. But in more recently, it's mostly because of opioid related death that has driven the increase in number of transplants.

Currently, we do about 4,000 to 4,500 transplants in the United States. However, that number was never going to be enough to support all the patients who need advanced treatment that have end stage heart failure. And the solution has always been mechanical heart and the development of a mechanical device that can support these patients long term. So, the first mechanical device, that was used, was a total artificial heart. But what you may not realize is that, a lot of that research that went into the development of that came from the Cleveland Clinic. So, Willem Kolff, he was the father of artificial organs, he developed the first dialysis machine. And most of that work was done here at the Cleveland Clinic and he had a center for artificial organs. And a lot of that research that went into the development of the first total artificial heart was done at the Cleveland Clinic.

So, the first device that became nationally recognized and FDA approved was the HeartMate XVE or what we call the HeartMate 1 in some places. And it's a very large device. It was a pulsatile device, it had two plates that moved and then pumped the blood through the patient. However, that device did work. It was a big bulky device, it had a drive line that comes out that's attached to batteries, but it did show efficacy. So in the trial it randomized patients to get the LVAD, the HeartMate XVE or medical management. And if you look at what happened to the patients that just got medical management, at one year, only one out of four patients were alive. And at two years, only 8% of the patients were still alive. So, when you have advanced heart failure, it was worse than any cancers you can imagine. It's worse than breast cancer, it's worse than colon cancer, it's worse than lung cancer. And when you had an LVAD, that first generation LVAD, your survival more than doubled. However, long term, because of how bulky these devices were and because of all the moving parts and all the complexity, these devices unfortunately just were not that durable. Very few of these patients survived more than two years.

So, over time, what the field realizes, we cannot have these big bulky devices. We need simpler devices with less moving parts. And less complexity, less moving parts, will ensure that you're going to have a more durable system. And that's where the HeartMate 2 came in. The HeartMate 2 had only one moving piece. It only had a single rotor that spun inside the housing. And as it spun, it sucked blood from the left ventricle, injected into the aorta. And that device really became the bread and butter heart failure device that we knew for the last 15 to 20 years. There's been over 10,000 patients that's been treated with the HeartMate 2, and it was really in the golden era of mechanical circulatory support.

The downfall of the HeartMate 2 was the fact that it still had two bearings. So, these two ruby bearings on which the rotor spun and the ruby bearing did create some heat. Even though the blood as it comes in was able to dissipate some of that heat, it really led the industry to develop the HeartMate 3 and the centrifugal pump in the HeartMate 3. And the HeartMate 3 really has been a revolutionary pump. It's a centrifugal pump, it is completely levitated by magnets. And as those magnets suspend the rotor in the air, it'll spin the rotor. And because of that, there is no moving parts, there is no parts of friction. So there is no friction at all, and the blood will just continuously get pumped with no friction. And because of no friction, you have no hemolysis. And this has been a design that has really brought mechanical circulatory support to the modern era and allows to achieve the results that we achieve today.

You have a drive line that comes out, it's attached to a computer, and that computer is attached to batteries. It's an efficient system. So, patients do need to change the batteries, but they just change it twice a day. And at night when they're asleep, they connect it to the wall. So, everything is suspended by magnets and which is the great design.

So, if you look at the advances in survival in this technology. So again, if we think back 20 years ago to the trial, at two years, if you had advanced heart failure, your chances of being alive is only 8%. Now, over time, medicines did get better. But even with the best medicines, now at two years, your survival is improved, but it's still only about 50%. With the HeartMate 3, in the early trials of the HeartMate 3, we got that two year survival up to about 80%. And now at two years, our survival is around 85%. And if you contrast that to heart transplantation, it is essentially on par with heart transplantation. So now, we have a disease that we have improved the survival from 8% at two years to 85% at two years. There is no other disease than medicine that have seen such a significant improvement in outcomes in the short period of time, 20 years. And more recently, the five-year outcomes of the HeartMate 3 trial, the MOMENTUM trial came out. And it showed that, at five years, the survival is about 60%. Now, it's important to remember that, when we think 60%, we think, "Well, why can't it be 100%?" It's important to remember that these are often older patients with multiple comorbidities. So, again, just to show you that you have such a deadly disease and we've gone so far with it, and we have outcomes now that rival many other treatments in cardiac surgery.

So, the LVADs still have issues that we need to overcome. And the four main complication rates with LVADs are pump thrombosis and failure, stroke, infection and bleeding. So, pump failure and thrombosis have now essentially been eliminated with the HeartMate 3 magnetically levitated design. If you look at the stroke rates, at two years for the HeartMate 3 in the MOMENTUM trials, it was about half, less than half of what it was for the HeartMate 2.

And if you look at our experience here at the Cleveland Clinic, at two years, our stroke rate's at 8%. And then on the most recent report, it's actually down to 5%. So at two years, the stroke rate is now down to 5%. So, if you look at the perioperative stroke rate, which is about 2%, once you've gone past the first 30 days, the ongoing rate of stroke if you have an LVAD is about one and a half percent. So, that's truly remarkable.

So, bleeding and infections are still a major issue. Bleeding, particularly with GI bleed is still an issue. However, with the HeartMate 3, it is less than the previous devices. We recently completed a trial called the ARIES trial. This was a trial comparing aspirin and Coumadin, which is the standard of care versus Coumadin only. So, the question was, whether or not Aspirin was necessary. We were the largest enrollers in the trial and the results came out and it showed that there was no difference in the pump thrombosis rates. And the patients who did not get aspirin, ended up having less GI bleeding. So, because of this trial, we no longer use aspirin for majority of patients. So, now you have a patient come up, you'll ask, "Why is the patient not on aspirin?" Now you know the answer why, because it's just not necessary.

The other issue that we have not been able to solve is that of infection, particularly with driveline infection. We have an interface between the skin where the drive line comes out, and often that is a source of trauma. If patients get their device caught on the door handle, or if it falls and it ends up pulling and it causes a skin laceration, often that then starts a process where bacteria gets in and they end up having driveline infections. Occasionally, we will need to do driveline i&d’s for these patients. That is one area that we still haven't fully solved.

The next generation of pumps is going to be completely internalized. So, instead of having any external components, the drive line is going to be inside the body and the battery is also going to be inside the body as well. And it's going to be charged just like you would charge your phone, you would have a charging pad at night and you put your phone on the charging pad, and now you're going to have the charger connected to your battery.

So, there's still some kinks to be worked out, but that is going to be essentially the next generation of devices that we're going to see. And that, in my estimate, will significantly decrease our rates of infection.

So, in conclusion, LVADs have seen a significant improvement in survival in the last 20 years, to the point where LVAD survival now is equivalent to that of heart transplant. I have patients who have LVADs now that are on the transplant list, and they come back and they tell me, "I feel perfectly great with my LVAD. I'm no longer interested in having another surgery. I want to be taken off the transplant list." It's not the majority. However, there's a lot of patients that do want to just live with their LVADs. Future improvements are targeted on quality of life. And with that, I want to thank you.


Thank you for listening. We hope you enjoyed the podcast. We welcome your comments and feedback. Please contact us at heart@ccf.org. Like what you heard? Subscribe wherever you get your podcasts, or listen at clevelandclinic.org/cardiacconsultpodcast.

Cardiac Consult

Cardiac Consult

A Cleveland Clinic podcast exploring heart, vascular and thoracic topics of interest to healthcare providers: medical and surgical treatments, diagnostic testing, medical conditions, and research, technology and practice issues.

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