Abstract
It is reported that a synchronized control of rotary left ventricular assist devices has some advantages in comparison with constant rotational speed control. The most common way to synchronize to heart beat is to use ECG signal because R-wave represents the beginning of systole and is easily detected. However, it is difficult to detect the onset of diastole. The aim of this study is to develop the algorithm to synchronize to heart cycle without external sensors such as ECG.In proposed method, a heartbeat was regarded as disturbance to pump rotational speed. Thus the disturbance was estimated as the difference between measured and estimated rotational speed. An ARX model which input was the reference of pump speed and current consumption was adopted to estimate the instantaneous rotational speed. The proposed method was tested in both a mock circulatory system and animal experiments. The results indicated that the system can output the heart cycle signal and detect not only the onset of systole but that of diastole. Furthermore, co-pulse and counter-pulse mode control can be demonstrated by using the detected timing. However there was detection delay at start of systole.
