Minimally invasive estimation of cardiac function for patients with rotary VAD support

Maximum ventricular elastance, E/sub MAX/, is a reliable quantitative index representing the contractual status of a patient's heart. However evaluating E/sub MAX/ usually requires invasive pressure and flow sensors, which only can be performed under certain clinical facility. If an indirect index of E/sub MAX/ can be identified from the measurements of a ventricular assist device (VAD) without any indwelling sensor, this would facilitate an effective way to monitor the healthy condition of the patient's heart while the patients are under VAD support. This index can also be used to determine the control strategy of VAD operation and gradually wean the patient from the mechanical circulatory support. In this paper, two possible indices, pump flow pulsatility and arterial pulse pressure, were evaluated as alternative representations of E/sub MAX/ using data from a computer simulation model of cardiovascular system with a HeartMat II left ventricular assist system (LVAS). Pump flow pulsatility showed a strong correlation to E/sub MAX/ regardless of pump speed changes, and thus can be used as an index for E/sub MAX/.