Artificial Heart – Parts 10, 11, and 12

A series of videos which talks about the Total Artificial Heart and the role it plays in therapy for patients waiting for heart transplant.

  1. Artificial Heart Videos Parts 1, 2 and 3
  2. Artificial Heart Videos Parts 4, 5 and 6
  3. Artificial Heart Videos Parts 7, 8 and 9
  4. Artificial Heart Videos parts 10, 11 and 12 (current post)

These videos have been provided to by (Peter Crown, Ph.D, Virtual Clinic Research Center) and the Summer Institute on Medical Ignorance, University of Arizona, College of Medicine.

10. How ejection and filling are monitored in the Total Artificial Heart?

The graphs that you see at the top, these are vitally important. We reference these all the time when we are looking at patients, how they are doing and what they are doing? Really what these graphs capture is they capture the airflow that I was talking about- the airflow coming out of the console, back in, out and in. This is the airflow that we are capturing. So what we look for on these graphs is on the left side- this is a pressure graph, on the right side you see a flow graph. So the left graph is used to assess that the device is fully ejecting- that the airflow that is going out has enough pressure there so that it pushes all the blood out of the device, through the body and into the lungs. And on that graph you will see a blue line and a red line. The blue line represents the right side of the device and the red line represents the left side of the device. In red here, we see pressures up to 200-250 on the left. And in blue over here we see pressures from negative 20 all the way up to 120. The blue is less than the left, and you might ask why is that? It is because the pressures that we need for the left side of the device to pump through the body is greater than the pressure we need to pump to the lungs and we will also demonstrate that. So what you are seeing on the pressure graph is what we look for is we look for this plateau what you see here. It is what we call an eject flat. What that means is as you trace this graph the valve is opening, there is flow through the device through the valve, and then right here at the end you see the eject flat which just lets us know that we are getting the last bit of the blood out and we are fully ejecting the device. So this is functioning properly right now.

On the right side of the graph here, this is the flow. This is where we assess how it is filling- is it partially filling or fully filling. What we look for here is we make sure that both left and right, red and blue lines here are horizontal to the X-axis all the way across. And as we see here again this is a good scenario left and right, both red and blue are horizontal along the axis all the way throughout. What we would see if the device was fully filling, these lines would do something we call a ski slope, they would dip down to the X-axis and we would literally see a hill or a ski slope which we would call it, and that would let us know that the device is fully filling.

11. Why is ejection fraction important in the Total Artificial heart?

So why is it that we want to make sure that the device is fully ejecting and only partially filling. The reason is we want as little blood contact with this device as we can have. The more time that blood has to interface or hang out with the device, it sees the device as a foreign object and then certain things happen there such as clotting. The longer the blood sees a foreign substance it may clot and then clots can be bad, especially if it goes to the brain or if it goes to the lungs. So  when we fully eject, what we are doing is that we are making sure that all that blood that was in the device is now gone, so it no longer has any time in the device. And as far as the partially fill, if the device full fills what would happen is that any time it full fills it has a moment where the blood in there stagnates and it is still and has more time with the surface of the device. So by partially filling and then fully ejecting, we are never giving it a chance to stagnate, so we are reducing the time that the blood sees the device.

12. What are the controls for the Total Artificial Heart?

The front console area of the device here that you see, I want to go over that briefly. This is where we make changes. So we assess the graphs, we see that there are some changes that need to be made, how do we make those changes? This is where we make those changes. The knobs that you see here, this would be the left pressure and this would be the right pressure. We would make changes here if we are having a problem with fully ejecting. So if we are missing the eject flats on our graphs, what we would do is we can up the pressure on the left, up the pressure on the right, either or both, whatever needs to be done. So that has to do with pressure and the eject flats.

In the middle here, this is where we would change anything that had to do with partially filling or fully filling. So if the device is full filling, we have a choice. We can increase the rate that the device is pumping, or we can increase the %systole. Now systole, you and I both with our normal hearts have both a systolic function and a diastolic function. Basically systole is when the heart contracts, diastole is when the heart relaxes. So if we increase %systole, it is the percentage of time the device is spending in the contraction mode. Again that means that there is less time for filling which would mean that the device would never have a chance to full fill and we would make sure that it is partially filling. So heart rate, %systole for full filling issues, left and right drive pressures for ejection issues. This is where we make those changes.

Here, this is our alarm panel on the console. As you can see with the alarm panel, there are more version of alarms than others. The yellows is letting you know that something needs to be changed on the device but not very important. Orange is getting a little more serious, all the way to red where it is absolutely serious and we would need to change something within minutes. Also on this side of the console you will see the vacuum. As I was saying earlier, there is a vacuum in this which is pulling the air pressure back putting the device in diastole. And we are able to do battery checks to make sure that the batteries are functioning properly. And then I have an alarm mute here to mute any alarms that we have.

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