This is a large left-ventricular
assist device, a bedside one. These devices
actually can be quite small and can actually
be basically in the chest with a pack
that you carry at your waist
and you can go home with them.
But, that's not a common situation.
The left-ventricular assist device is placed by
a cardiac surgeon. It has a balloon that inflates
during cardiac diastole. So, when
the heart is relaxed, the balloon
in the left-ventricular assist
device inflates. And we'll see in
a subsequent slide that this actually increases
diastolic pressure in the aorta, which improves
coronary blood flow, and improves oxygenation
of the heart, so that's good for the heart muscle.
Then, during cardiac systole when the heart contracts,
the balloon in the left-ventricular assist device
deflates. That unloads the pressure
against which the heart has to work,
improves cardiac output and produces
less work for the myocardium. This kind
of device is often used to stabilize
patients prior to cardiac surgery. And
it can actually be used, as I mentioned earlier,
as a bridge to heart transplant. And the smaller
devices that can be implanted are used temporary
as artificial hearts, and people can
use them for up to several months before they,
before they start to have problems with them.
And this is a diagram of how this device works.
You can see that the balloon, which is
the gray device in the aorta, comes all the way
up almost to the heart, just to
where the left subclavian artery comes off.
And it inflates during diastole
increasing the pressure in the blood close to the heart,
forcing it into the coronary arteries and
improving myocardial oxygenation. And then
during cardiac systole it deflates, so that
the pressure against which the heart is working
is markedly reduced and the oxygen demands
to the heart have reduced. And sometimes
this can result in complete recovery
of the heart. The ECG is modified
and you have to learn how to
to utilize this device, and you have to learn
how to set the device to inflate and deflate
at the right times. If you're off by even just half
a second or so, you can cause a lot of problems.
So it takes highly skilled people to use this