So, I am just going to go through different applications of ventricular assist devices in patients having valve disease. You can use it as a backup for high-risk surgery; you can use it preemptively for postcardiotomy as an alternative to high-risk surgery and some other novel applications. So, by ventricular assist devices, we generally mean temporary assist devices, such as this. This is as Thoratec CentriMag pump which is probably the most frequently used short-term device in the United States now. There are other devices like the Abiomed device, which some of you might have in your centers. Some centers use ECMO, extracorporeal membrane oxygenation, some use the TandemHeart, and there also are the older Thoratec devices.
So, the first application is a back up for high-risk surgery. Basically, these are patients who are going to have conventional heart surgery but are very high risk of developing post cardiotomy shock. Patients with very low ejection fractions having a very long ischemic time, a long cross-clamp time, and you do surgery with a plan to place an assist device if you cannot come off the heart-lung machine. Once you plan preemptively it is much better than doing it in an emergency when the patient is very sick.
This is an example of such a case. This was a 50 year-old male patient who was an immigrant from West Africa, did not have insurance, so he was not a transplant candidate. He has got a lot of aortic regurgitation, a lot of mitral regurgitation, an EF of about 10%, very dilated ventricle; 8.5 mm, severe pulmonary hypertension, PA pressure of 75. This is a patient that ordinarily you would refer for transplantation, but because he cannot have a transplant, we decided to offer him triple valve surgery. So, in such a case, you do the surgery, you have the ventricular assist device in the room, if you cannot come off the heart lung machine you put the patient straight on the device. He actually did well and he did not need a device and his ventricular function actually improved marginally and the size of his ventricle came down 6 to 7. He eventually died about 20 months later of multiorgan failure. He came into hospital in cardiogenic shock and died but he did get about 18 months of good quality of life.
The second use is preemptively. So this is going a step forward. We have a patient like this and we say we are not going to try and come off the heart lung machine, we are just going to put in an assist device. The patients that we do this in, is essentially the same as the first group; people with severe ventricular dysfunction having conventional surgery. So, you decide before how you are going to put a VAD and then you take it out in a planned fashion either days or weeks later, and the rationale for doing that is that the alternative for all these patients as you see in your hospital is they come out of the operating room on high doses of epinephrine, norepinephrine, Milrinone, balloon pumps. They are on so much medication they get vasoconstricted, sometimes they get ischemic guts, they get ischemic limbs, they go into kidney failure and as an alternative to that you can switch off all those ionotropes and just put in a ventricular assist device. It will give you good flow, good perfusion, you do not have to go on high-dose pressors and ionotropes. So, in the immediate post-op phase you have good tissue perfusion and you can rest the heart. So the heart is off-loaded, it rests, and it can recover from whatever the trauma of the operation was.
The type of device you put in depends on how long you think the recovery will take and the likelihood of recovery. If you think that the heart is going to recover within days you can use a CentriMag, or a TandemHeart; simple devices you take out within a week of surgery. If you think it is going to take several weeks then there are other devices you can use like the old Thoratec devices that you can leave in for weeks or months, but importantly if you think that this is a patient that you are not sure; 50/50, he may fly, he may not fly, then put a device that you can leave in for ever, like a HeartMate device, an implantable device. So, if you cannot wean them then you do not need to do any more surgery. Just leave them with a device either as a long-term, lifetime device or you can bridge them to cardiac transplantation.
Here is an example of such a patient. He is 65 years old. He has two previous bypass operations, very poor biventricular function with severe mitral regurgitation. So, we offered him a mitral valve repair but in that case we decided electively we would put in an assist device. So, he had a TandemHeart placed and we placed this through the axillary artery. He has had his surgery through a thoracotomy. This is the head of the patient. This is his abdomen here and you can see the tubes from the device coming from his right shoulder. This is the surgical incision to replace the valve and this is the pump, which is a centrifugal pump, and we left that in him for four days. The advantage of that is that the patients can actually sit up in the bed with this. It is not like when you have the TandemHeart in the groin there, sort of have to lie down. This is the patient getting ready to have the device taken out and it is just taken out under local anesthetic. So, he does not need to be put to sleep to take this out. We just open this small incision here; control the vessels and take it out. The patient did very well and was back to work as an accountant within three weeks. We published just recently; had this accepted for publication; this technique and we have done it in about four patients so far.
The postcardiotomy shock is the use that most of you would have seen in valve surgery and it is probably the one we should discourage the most, but basically it is people who cannot wean off the heart lung condition, if you have had a cardiac arrest in ICU and if you are in shock, so the shock is your hypotensive low index; and you are not responding to ionotropes and you have to exclude things you can treat; like if a bypass graft has gone down or cardiac tamponade. Those are things that you should treat first but most importantly you have to exclude irreversible causes. So, if the patient suffered some major catastrophe in the operating room, the heart is not working, there is a stone heart, the heart will never ever, ever, ever recover. You can put in as many LVAD's and BiVAD's and ECMOs as you like, they are not going to get better. It is a futile exercise and it is important to exclude those patients, putting in a VAD for postcardiotomy shock. And the patient should otherwise be salvageable. So, it should not be a patient who has got terminal cancer, 85 years old. You have to do it in someone who you think there is a chance, who will succeed, but most importantly the prognosis is poor. This is data published from Medicare; data a few months ago which showed that patients in postcardiotomy shock at one year; only about 27% were alive. So, three and four patients will die and of those alive many of them have severely impaired quality of life and it costs a lot of money. So, it is something that we question whether we should do. Ideally you would want to put in the VAD's preemptively in these patients before they deteriorate so significantly and go into multiorgan failure and in that way you might be able to save some of these patients.
The fourth application is an alternative to high-risk surgery and this comes about because we now have better ventricular assist devices. This is a paper published in the New England Journal last year about a HeartMate II device which is an implantable device, put in the abdomen, connected to the heart. It is a continuous flow device, a second generation device and this device can be put in with very low mortality and indeed very good outcome. Six months after implant in this study, this was the FDA study, 85% were either alive or had transplants. So, this device has revolutionized ventricular assist device therapy and the question then arises; if you have a patient that is very sick who is going to have conventional surgery, you do a very good operation, they survive, many of them do not live that long, or they do not have a good quality of life, the question is whether you should just put an assist device as an alternative to doing surgery because often you fix the valve you do not fix the ventricle, they still spend the rest of their life with a 15% ventricle, they will still have symptoms, they still will not be able to do a lot of what they want to do and there is an example of a patient we operated on just last week.
He is a 64 year old with severe aortic stenosis and moderate mitral regurgitation, ejection fraction 15%, very dilated ventricle, severe RV dysfunction. So, we could repair his mitral valve, replace aortic valve, repair tricuspid valve but he is not going to go very far. The best thing for him would be to put an assist device, which is what we did. We put an assist device. He is doing fine. He is going to go home on Monday and he will have a good quality of life and since he is 64 he can be considered for heart transplant and at the end of the day you probably save more patients by doing this then embarking on heroic operations, and we all sort of feel good that the patients survived, they left hospital but really it means nothing, I mean surviving is not the key in this kind of patient. It is your quality of life and how long you live in the long term, not whether you survive surgery.
So, the fifth indication is not one we have done much but is popularized by the group at Texas Heart. Basically, if you have patients in cardiogenic shock, they come to the cath lab or emergency room; let us say they have a ruptured papillary muscle or post infarct VSD. Rather than rushing them to surgery to do salvage operation just put in an assist device and see how they do. So, they put in an assist device through the groin in the cath lab like a TandemHeart or put them on ECMO, give them a few days, let them wake up, let their liver get better, kidneys get better and if they look salvageable then go and do the major surgery. It is something that can save a lot of resources ultimately because it saves you having to invest in a lot of surgery and saving people that cannot be saved. Then at the end you are left with those that recover and then you can go ahead and operate on them.
The sixth I will not dwell on; this is just dealing with complications of surgery and sometimes when there are some complications it is better to rest the heart for a few days and you can use an assist device for that.
So, I will just say very little about the postoperative care which is that these patients are different from other heart surgery patients once they have an assist device and it becomes very important to maintain their volume quite tightly, if they come out on just a single ventricular assist. If you overload the body, the other ventricle can struggle. The afterload is very important because you need tissue perfusion, and if it's too high, because the pumps have to pump against the afterload. So, if you have a left ventricular assist device and you are hypertensive with a systolic blood pressure of 140, the flow of the device would be low. You have to maintain that. You will have to support the unassisted ventricle with ionotropes, give nitric oxide for the lungs, and optimize the heart rate but most importantly; bleeding. You have to reexplore them if they bleed. You do not watch this kind of bleeding because they go into tamponade very quickly and the tamponade affects the fitting of the ventricular assist device and affects the other ventricle.
In terms of weaning, we wean the patients when there is no organ dysfunction. So, the kidneys are working, liver is working, brain is working, lungs are working. There has to be good tissue perfusion so the patient is well perfused, in that they do not have black legs, ischemic legs, they do not have ischemic gut. There should be no acidosis. They should be passing urine. You turn the VAD flow down, you do an echo. The echo should show at least moderate ventricular function. You cannot be perfect on everyone because many of these patients are very sick. So, you are not looking for a 50% ejection fraction, 30% you'd take. Then once you see that, you start weaning down the VAD over a period of usually 24 to 48 hours, sometimes longer, you heparinize the patient fully to reduce the chances of thrombus and then if that is all successful you explant the patient.
Often, I must say though that a lot of the patients, quite a few that we have seen, we explant them successfully but some of them will still go and then die of low output syndrome or multiorgan failure. So, the salvage rate is not always high. If you cannot wean them, they'll usually die and you would have to speak to the families and involve palliative care and discuss end of life. It is often traumatic because unlike other forms of death this is one form of death where it can only happen if you actively do something; which is switch off the machine. So, it is very difficulty for families to take, which is another reason why it is important not to put these devices in patients that you think have no hope at all because it is just making a more difficult situation even more difficult for the families. Some patients, if you cannot wean them, can be transplanted, but that is a minority, and then some patients can be converted to long-term devices but that is even a smaller minority for the reason that most patients who cannot wean are also in multiorgan failure and very sick patients.
So, in summary, something useful for high risk valve surgery but it is really a niche intervention, it is something that is probably less than 1%; 1 in a thousand patients should get, but where we use it, we should consider using it early. For postcardiotomy shock its use should generally be discouraged because the results are universally poor. In my institution we do about 40 to 50 ventricular assist devices a year, so it is a sizable program, and in the last three years, we probably had 20% of patients survive postcardiotomy shock, and that is with an experienced team, so it is not something we should be doing too often. Thank you.
- An excerpt from Dr. Anelechi (Ani) Anyanwu's video presentation at the 46th Annual Meeting of the Society of Thoracic Surgeons.
- An excerpt from Dr. Javier Castillo's video presentation at the 46th Annual Meeting of the Society of Thoracic Surgeons.