A mechanical heart

18 December 2018

Interview with

Stephen Pettit, Royal Papworth Hospital

Heart attacks can be devastating, and the scarring that's left makes it difficult to live a normal life afterwards. So what can be done? Chris Smith spoke to Stephen Pettit from the Royal Papworth Hospital, he’s a cardiologist with a speciality in advanced heart failure, after first hearing from Sarah Miles, who's recovering from a heart attack.

Sarah - I was working as a nurse but became unwell. I was diagnosed with diabetes and angina. My symptoms got worse and I was repeatedly told the cause was anxiety and depression. But I suffered a heart attack, which led to a cardiac arrest. I was only 38 and the damage was severe. Most days just washing and dressing is enough to exhaust me. I spend more hours asleep than I do awake. The whole body fatigue and breathlessness is overwhelming and I'm no longer able to sleep in my own bed as the stairs are just too much to manage. I've been referred for a transplant or possible LVAD, a mechanical heart. My GP of over 20 years manages most of my care, which is an incredible support. The British Heart Foundation has been incredibly supportive too and I work voluntarily with them to raise awareness, which I think is very important especially with the younger generation. I always felt I had a story to tell, an experience to share and a voice to be heard. They have given me that opportunity and now a purpose for which I will be forever grateful.

Chris - Sarah Miles. Thank you Sarah. So why can't the heart regenerate like the liver does? With us is Stephen Pettit, he is from the Royal Papworth Hospital in Cambridgeshire. He is a cardiologist specialising in heart failure. When a person has a heart attack, Stephen, what actually happens to the heart muscle?

Stephen - The medical term is myocardial infarction and occurs when a coronary artery becomes blocked. This is normally recognised one would hope quite quickly and great efforts are taken to reopen the artery and restore blood flow to that part of the heart. But if that isn't done or if that's not successful then that part of the heart unfortunately becomes sort of irreversibly damaged by the heart attack.

Chris - And that means you lose heart cells from that part of the organ?

Stephen - Yeah absolutely, so heart muscle cells are not able to sort of divide and regenerate. The heart heals, but in healing scar is formed and scar cannot contribute to the sort of contractile function of the heart. So the pumping function will go down and scars can cause other problems in hearts as well.

Chris - So you end up with a stiff scar which is presumably a compromise - I need to heal this damage up quickly, so I lay down a fibrous scar, which seals the breach in the heart, but you've lost the contractile part, the heart muscle. So as you say the heart loses its pumping ability and that's why patients, like Sarah whom we heard from, get heart failure. Their heart just can't produce enough effort to push enough blood fast enough.

Stephen - Yeah absolutely. I mean to a certain extent there are medications that can mitigate against this sort of progression of heart failure, but absolutely there is no way back at the moment from that process of scar formation in the heart.

Chris - What can we do for people in that situation at the moment then?

Stephen - The mainstay of treatment for people who have developed heart failure is tablet treatment. Tablets can produce enormous improvements in how people feel and also led to a revolution in how long people survive with heart failure. But at the extreme end of the spectrum, when tablet treatment is not enough and despite that people are feeling awful and people's outlook is poor, then we turn to more extreme things, such as heart replacement therapy.

Chris - What sorts of things can you offer people?

Stephen - Well there are all sorts of options that are open now. Areas of scarred heart muscle are potential source of rhythm disturbances, potentially life threatening rhythm disturbances, so people with large areas of scarred heart muscle are sometimes offered implantable devices called defibrillators. They're a little bit like pacemakers but they can act to automatically identify and treat rhythm disturbances that would otherwise be fatal. At Papworth Hospital we also undertake heart transplantation, which for many decades now has probably been the gold standard treatment for very advanced heart failure.

Chris - Before someone reaches the stage of having a heart transplant or perhaps even while they're waiting, is there anything apart from tablets you can offer that gets them slightly better function in the meantime and a better quality of life?

Stephen - Yes. For a proportion of people we will turn to something called mechanical circulatory support and that is using a mechanical pump to sort of maintain blood flow around the body while a person is waiting for a heart transplant. And the type of pump that we use most often are called Left Ventricular Assist Devices or LVADs.

Chris - Is that what you've got there in front of you?

Stephen - Yeah absolutely. So this is a an LVAD. There are three main bits to this. The pump, and the pump is implanted by one of our cardiac surgeons and it actually sits inside the chest. It sits right at the apex of the heart.

Chris - It's about the size of a small computer mouse.

Stephen - I mean it fits in the palm of a hand. They're really pretty small now compared with what they used to be.

Chris - Can I have a feel of it?

Stephen - Of course.

Chris - So this is metal. What’s it made of?

Stephen - Yeah. Its metal and inside it basically looks like the propeller on the back of a boat. In the most modern VADs that propeller is magnetically levitated, so there's no axle, there’s no ball bearings, there is nothing that would create friction. So blood cells flow incredibly smoothly through the VAD.

Chris - As I said this is about the size of a small mouse that you would use to use your computer with. It's got several portholes on it. One's in the front face. One's in the one side of it. So is that where the blood goes in and goes out.

Stephen - The blood gets sucked into the VAD through a very short metal pipe and there's then a flexible pipe through which the blood is pumped along and that flexible pipe, it gets called the outflow graft, is attached to the aorta of the patient. Then the third essential thing is a power supply. So the VAD needs a constant power supply and there is an electrical power cable that is tunneled along the anterior abdominal wall and exits through the skin. Then patients have a controller and battery packs they're attached to, so when they're connected to power they've got as much freedom as you or I - they can just go about their business.

Chris - So it pulls blood out of the left ventricle the main pumping chamber of the heart and then shoves it into the aorta. So the heart can continue pumping as normal it's just some of the stuff that it would pump is being taken off its shoulders if you like and put through this VAD device and into the main blood vessel instead.

Stephen - Exactly. And that's why they're called Left Ventricular Assist Devices. These do not take over the function of the heart completely but they do a substantial proportion of the heavy lifting.

Chris - How much juice does this use? I mean how energy hungry is this thing?

Stephen - Not particularly. I mean they'll typically have a power consumption of sort of three or four watts.

Chris - And the power supply - do people wear that or can that be implanted or how does that work?

Stephen - At the moment the power supply is outside. A person has normally a waist belt that will have the controller for the VAD and then two batteries. But this is all fairly small as well. If a person had a jumper on or was wearing a coat you wouldn't know that they were attached to all this. You need to be a little bit careful going through airports.

Chris - How much function can this make up for? I mean how good are these in practice?

Stephen - We typically see them pumping somewhere in the region of four to five, sometimes even six, litres per minute of blood, which would match the cardiac output at rest. .

Chris - Indeed. I remember seeing on Star Trek. because Jean-Luc Picard, he actually had an artificial heart and the heart that he had that was displayed once was bigger than that. So it's amazing to think you know, here we are about 20 years after that program was made and we're looking at a device that looks a very very similar to that but is smaller and clearly can do what they were saying was sci fi.

Stephen - Yeah. I mean there's some other sort of fascinating things about them. Early VADs used to generate pulsatile blood flow, but people quickly realized that actually that was traumatic to the blood and left patients at risk of things like stroke. So now VAds are continuous in flow. Once a patient has got one of these VADs implanted, the vast majority of them loose all pulsation.

Chris - So you have a pulse-less patient in front of you.

Stephen - Yeah absolutely.

Chris - That's a bit disconcerting isn't it.

Stephen - Blood flows continuously around the body and actually measuring things like blood pressure becomes really challenging because that normally relies on pulsatility.

Chris - Given how good you say these are. Do you think we're almost in an era then where actually, when someone with a heart problem comes to see you in the future, you're not going to bother with heart transplants you're going to give them the next generation one of these.

Stephen - Well that's a very very interesting question. Certainly the most modern LVADs have outcomes, you know two years post implant, that are pretty much the same as outcomes after heart transplantation. But we've only been using these pumps for a couple of years, whereas we know what happens 10, 15, 20 years down the line following heart transplantation. So certainly they're short and medium term outcomes are getting to a point actually where they're almost as good as heart transplantation, but in the long term, at the moment you know, there's a lot more uncertainty.

Chris - I mean it looks pretty basic. I'm sure the engineering in here is humongously expensive. How much does one of those cost?

Stephen - You looking in the region of sort of 80 to 90 thousand pounds for the LVAD itself and then there's all the sort of associated costs of implanting them as well. These are not cheap by any stretch of the imagination.

Chris - To contrast that how much does it cost to heart transplant somebody?

Stephen - Probably in the region of 20 to 30 thousand pounds for a heart transplant and the first year of care that follows. A heart transplantation is, at the moment, cheaper than support with the Left Ventricular Assist Device.

Chris - But given how common we think that heart disease, heart failure and so on is going to be in the future and given how few transplant organs we have at the moment, that we have access to, it looks like these are definitely going to be a big part of what we do in the future these Ventricular Assist Devices.

Stephen - Yeah absolutely. I mean if you look at National Statistics, the number of Left Ventricular Assist Devices that are being implanted is just going up year on year for exactly that reason. So I think these are gonna be a big part of the future of advanced heart failure.

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