A unique left-right flow imbalance compensation scheme for an implantable total artificial heart

A new method has been developed for accommodating the difference between pulmonary and arterial flows in a totally implantable, hydraulically actuated total artificial heart (TAH). The left and right sides are alternately pumped, with concurrent filling of one pump and ejection from the other. A small hydraulic fluid chamber is used to compensate for the higher left sided flow. This chamber is incorporated into the left inflow of the TAH, with the flexing bladder in contact with atrial blood, and the hydraulic fluid communicates with the right sided hydraulic chamber. The volume of hydraulic fluid that enters and exits the latter chamber constitutes a corresponding reduction in the right sided blood chamber stroke volume. Placement of this compensation chamber in the left side inflow provides a negative feedback of the right sided flow, based on the left atrial pressure (LAP). Higher LAP (indicating too much right sided flow) leads to higher fluid flow to and from the compensation chamber and a lower right sided blood flow and vice versa. The hydraulic flow resistance can be preadjusted to yield a 15% flow difference at an LAP of 15 mmHg.