Minimally invasive estimation of systemic vascular parameters for artificial heart control

Systemic vascular parameters are important indices of heart condition, incorporating these parameters into the control of a ventricular assist device (VAD) would facilitate the implementation of an effective control strategy. In order to minimize the need for indwelling sensors for obtaining these parameters, an estimator was developed to identify the systemic vascular parameters (characteristic resistance, blood inertance at the aorta, systemic compliance, and systemic resistance) using measurements from the Novacor left ventricular assist system (LVAS) and arterial pressure. Systemic compliance was estimated by the ratio of the LVAS pump stroke volume to the arterial pulse pressure and systemic resistance was calculated by the ratio of mean arterial pressure to LVAS pump output. These two parameters were then used as known parameters in an extended Kalman filter to identify the other unknown parameters using LVAS pump volume and arterial pressure measurements. Performance of the estimator was evaluated using data from a mock circulatory system experiment. The results showed that the estimates converged more accurately in a limited time when arterial pressure was used with the LVAS pump volume as measurements. These parameter estimates can provide diagnostic information for patient and device monitoring and can be used for future VAD control development.