A mathematical model to predict the optimal control mode for a pusher-plate total artificial heart (TAH)

Table I lists the physiological criteria for ranking each control mode (hemodynamic conditions assumed are listed in Figure 4). For each criteria, each mode was given a ranking of 0 to 3, with 3 the best. At the bottom of the table is the total of all criteria grades. The ranking from best to worst mode is in order: IND, LMA/LMS, Low FR/High FR, RMA/RMS. A discussion of Table I follows: FR is a reliable control mode and has been used extensively clinically, including the recent TAH human implants. The advantage of this mode is its simplicity: if the venous return is below pump capacity, then all incoming blood can be pumped out without any sophisticated controller. However, when the flow demand exceeds the pump capacity, HR must be increased. The ideal situation would be to set FR at one HR and %S, and leave these settings over the life of the recipient. However, a high HR like this would result in relatively high atrial pressures and low flow rates with respect to IND (as shown theoretically, in vitro, and in vivo). Although the patient would have a high maximum COR, the daily COR would be low, resulting in a relatively high AVO2 difference. Finally, FR lacks afterload sensitivity. RMA and RMS received the lowest grade of all modes. Because of the L-L shunt, the stroke length of these modes are smallest, and thus the CO curves and FPS are poorer than any other mode.(ABSTRACT TRUNCATED AT 250 WORDS)