Right ventricular assist system feedback flow control parameter for a rotary blood pump

At least 25-30% of patients with a permanent implantable left ventricular assist device (LVAD) experience right ventricular failure; therefore, an implantable biventricular assist system (BiVAS) with small centrifugal pumps is being developed. Many institutions are focusing and developing a control system for a left ventricular assist system (LVAS) with rotary blood pumps. These authors feel that the right ventricular assist system (RVAS) with rotary blood pumps should be developed simultaneously. A literature search indicated no recent reports on the effect of hemodynamics and exercise with this type of nonpulsatile implantable RVAS. In this study, a calf with an implantable right ventricular assist system (RVAS) was subjected to 30 min of exercise on a treadmill at 1.5 mph, resulting in excellent hemodynamics. The input voltage remained unchanged. Hemodynamic recordings were taken every 5 min throughout the testing period, and blood gas analysis was done every 10 min. Oxygen uptake (VO2), oxygen delivery (DO2), and oxygen extraction (O2ER) were calculated and analyzed. Two different pump flows were investigated: Group 1 low assist (<3.5 L/min) and Group 2 high assist (>3.5 L/min). In both groups, the RVAS flow rates were unchanged while the pulmonary artery (PA) flow increased during exercise; also, the heart rate and right atrial pressure (RAP) increased during exercise. There were no significant differences in the 2 groups. The PA flow correlates to the heart rate during exercise. In all of the tests, the VO2 and DO2 increased during exercise. Regarding VO2, no changes were observed during the different flow conditions; however, the DO2 of Group 2 was higher than that of Group 1. Because the implantable RVAS did not have pump flow changes during the test conditions, it was necessary to incorporate a flow control system for the implantable RVAS. During exercise with an implantable RVAS rotary blood pump, incorporating the heart rate and VO2 as feedback parameters is feasible for controlling the flow rate.