Unlike the natural heart, the Jarvik 2000 pump does not “beat.” Instead, it uses a spinning rotor to propel blood from the left ventricle into the aorta. But the natural heart continues to contract and relax, and the volume of blood moved by the spinning rotor rhythmically increases and decreases in synchrony with those contractions.
Jarvik 2000 patients do, therefore, retain a pulse. The Jarvik 2000 magnifies the blood output of the heart, effectively producing a pulsatile blood flow in concert with it. The device truly assists the patient’s own heart without hindering it. With both the biological heart and the mechanical pump moving blood into the aorta, the congestion of fluids brought on by heart failure can quickly subside.
Miniaturized technology has allowed the Jarvik 2000 pump to be made small — so small that it is implanted inside the left ventricle of the biological heart. The pump is inserted through a circular incision in the heart wall and secured with a polyester sewing cuff. A fabric tube from the outflow end of the pump connects it to the aorta.
This type of device is sometimes called a “booster” pump. By supplying some — but not all — of the blood flow to the aorta, the pump boosts the performance of the natural heart to stabilize blood pressure, normalize blood flow to the body, and relieve fluid congestion in the body, all the while allowing the natural heart to fill with and eject blood.
Control of the Jarvik 2000 FlowMaker® is placed in the hands of the patient. Jarvik 2000 patients must therefore monitor both themselves and the device to some degree. Unlike the natural heart, mechanical devices do not “know” with certainty when patients exert themselves and need more oxygen-rich blood to the muscles; neither do they know when patients are sleeping and need less. Depending on the heart’s condition and the patient’s level of activity, the output (i.e. rotor speed) of the Jarvik 2000 can be adjusted to accommodate patient needs using a small, external controller.
We believe that the manual-control approach of the Jarvik 2000 FlowMaker® remains the safest approach to regulating a VAD. Some other heart rotary assist devices have automatic control systems in which a computer determines the speed of the pump. This works in some circumstances, but there can be situations in which the computer can make a mistake and run the device at a dangerous speed because it does not have enough information about the patient’s condition.
With the Jarvik 2000, Patients receive guidelines for making adjustments to the pump’s speed, but over time, they learn to adapt the settings to their individual health conditions. Improvement in heart function, for example, can prompt gradual changes to their settings. Most patients need only to adjust the pump speed occasionally, and they often “feel” the need to turn the pump up when exercising or down when at rest or going to sleep. The five speeds of the Jarvik 2000 FlowMaker® afford the patient a considerable range for rest and exercise but does not permit unsafe extremes.