How Does the Impella Ventricular Assist Device Work?
Impella is a ventricular assist device, that is FDA approved for short-term support of the left ventricle. There is also a version that can be used for the right ventricle as well. The device can support 2.5 to 5 L/min of blood flow, the latter of which is considered a normal cardiac output.
The device is minimally invasive and catheter-based, so it is usually placed by Interventional Cardiologists in the catheterization laboratory. It is an impeller driven, axial-flow pump (which derives its inspiration from the Archimedes pump from antiquity).
The device is positioned so that the intake of the pump sits in the LV cavity and the outflow in the aorta, just above the aortic valve. In this way, the pump replaces the work done by the left ventricle and sucks up the oxygenated blood as it returns from the left atrium and forcibly delivers it into the aortic root (beginning part of the aorta).
The oxygenated blood then feeds the coronary arteries and the rest of the body. By removing the blood from the LV cavity, the device reduces pre-load, and by ejecting it at a high velocity into the aorta, it reduces afterload. This has the net effect of “unloading” the left ventricle and thereby reducing the energy required by the LV to function. This, then, rests the LV and allows it to recover as the LVAD does the heart’s work. An impella placed in the RV works by the same principles, to help right ventricular function.