So far, we have proposed the control algorithm to synchronize output of ventricular assist device to native heart cycle without external sensors such as ECG. In the method, heartbeat component in pump rotational speed was regarded as disturbance to controlled rotational speed. Thus the heartbeat signal was calculated as estimation error of rotational speed. Moreover this signal seems to have also information of native heart function. Therefore, the aim of this study is to attempt to estimate cardiac function from the estimated heartbeat signal.The instantaneous pump speed was estimated by an ARX model which inputs were reference speed and current consumption. The parameters of the model were calculated by using recursive identification algorithm.In results, some features of the estimated heartbeat signal have a close relationship with circulatory parameters. Therefore, it was indicated that the proposed method may be able to estimate not only cardiac cycle but function.
