Vascor’s Device
A Real Ventricular Assist Device (VAD)
Rotary VADs propel blood in parallel with the heart’s left ventricle and frequently inhibit the left ventricle from normally pumping blood through the left ventricle’s outlet aortic valve. When this occurs, all of the circulation’s blood flow goes through the VAD and the VAD may more properly be termed a ventricular replacement device as opposed to a ventricular assist device.
Vascor’s VAD will be placed in series with the heart. As such, it will be a real assist device that will provide a number of potential advantages. First, if for any reason, pump power is lost or turned off there will be no risk of reverse blood flow through the pump into the weak left ventricle as mentioned above. Secondly, Vascor’s pump operates by expanding its blood volume during the ventricular contraction phase or systole, making it easier for the weak left ventricle to empty its blood contents into the aorta. Then, when the ventricle is resting and filling with blood during diastole, the pump’s blood volume is decreased, forcing blood through the peripheral circulation and adding circulatory work to supply additional blood flow to the body. This combination of increasing and decreasing pump volume in synchronization with heart function is termed counterpulsation.
Counterpulsation is a well known real form of heart assist. On a temporary basis, tens of thousands of patient’s hearts each year are assisted by intra-aortic balloons that operate using counterpulsation. The animation below illustrates the counterpulsation principle used in Vascor’s pump design:
The Vascor LVAD is under development and has not been approved for sale or use by the U.S. Food and Drug Administration (FDA).
What Is Heart Failure?
The American Heart Association defines CHF as the inability of the heart to satisfy the blood flow needs of the body. CHF afflicts an estimated 5.4 million Americans. The New York Heart Association or NYHA defines the severity of CHF by Classes from Class 1 through Class IV. Class IV is the most severe CHF form wherein the patient suffers shortness of breath at rest and Class III CHF patients experience shortness of breath with mild exercise.
What Is an LVAD?
A highly successful solution for Class IV CHF is a heart transplant except that the annual number of available donor hearts in the US is limited to ~2,300.
Left ventricular assist devices or LVADs or VADs pump blood from the heart’s main pumping chamber, the left ventricle, around the heart and its main outlet valve, into the aorta, increasing the blood supply to the body. Each year, about eight thousand VADs are implanted worldwide. Today’s FDA approved and commonly used VADs are rotary pumps that propel blood by spinning blades. These spinning blades subject the patient’s blood to shear forces that in turn increase the likelihood of stroke from blood clotting. To prevent blood clotting, VAD patients receive anticoagulation medication but such medication risks episodes of bleeding which also can cause strokes.
On the positive side, VADs clearly prolong the life of Class IV patients but on the negative side, VADs have a number of adverse event types. In addition to strokes caused by clots or bleeding, clotting in the pump itself can occur and infection along the skin piercing VAD drivelines are significant and there is a mortality risk, if for any reason, a rotary VAD loses its electrical power. This is because without power, blood can flow backwards through the rotary pump from the high pressure aorta into the weak left ventricle.
