Balancing the ventricular outputs of pulsatile total artificial hearts.

BACKGROUND: Maintaining balanced left and right cardiac outputs in a total artificial heart (TAH) is challenging due to the need for continuous adaptation to changing hemodynamic conditions. Proper balance in ventricular outputs of the left and right ventricles requires a preload-sensitive response and mechanisms to address the higher volumetric efficiency of the right ventricle. METHODS: This review provides a comprehensive overview of various methods used to balance left and right ventricular outputs in pulsatile total artificial hearts, categorized based on their actuation mechanism. RESULTS: Reported strategies include incorporating compliant materials and/or air cushions inside the ventricles, employing active control mechanisms to regulate ventricular filling state, and utilizing various shunts (such as hydraulic or intra-atrial shunts). Furthermore, reducing right ventricular stroke volume compared to the left often serves to balance the ventricular outputs. Individually controlled actuation of both ventricles in a pulsatile TAH seems to be the simplest and most effective way to achieve proper preload sensitivity and left-right output balance. Pneumatically actuated TAHs have the advantage to respond passively to preload changes. CONCLUSION: Therefore, a pneumatic TAH that comprises two individually actuated ventricles appears to be a more desirable option-both in terms of simplicity and efficacy-to respond to changing hemodynamic conditions.