Abstract
Although the clinical application of LVAD has started, we have only a little knowledge on the hemodynamic changes during LVAD pumping. The interaction between the natural heart and LVAD was investigated through the entrainment of the heart rate by LVAD asynchronous pumping.
Sinus rhythm was monitored in LVAD implanted dogs and sheep while changing the pumping rate. The entrainment of sinus rhythm by LVAD pumping was observed in anesthetized dogs and also awake sheep. Namely, sinus rhythm varied according to the change in pumping rate when the pumping rate was approximately equal to or half the sinus rhythm.
To explain the discovered entrainment, computer simulation was performed. The macroscopic model of 'External periodic force and Self-oscillatory system' was used, since it has been known to induce the entrainment. In the model SA node was assumed to be a self-oscillatory system and LVAD an external periodic force. The SA node was also assumed to have the characteristic that sinus rhythm changes depending on the phase when neural impulses happen to arrive at the SA node. The computer simulation showed the similar modification of sinus rhythm by LVAD pumping to that in experiment.
The above gives us some idea of the control system of the heart and, moreover, LVAD is a useful tool for the physiological investigation.
