Minimally invasive identification of ventricular recovery index for weaning patient from artificial heart support

Maximum ventricular elastance, E/sub MAX/, is a reliable quantitative index of the contractial state of the ventricle. It is a strong candidate to determine the healthy status of the patient's heart. However, estimating 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 using measurements from 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 patient is under VAD support. This index can also be used to control the VAD to gradually wean the patient from the mechanical circulatory support. In this paper, three possible indices, systemic vascular resistance, maximum VAD inflow acceleration rate, and the maximum VAD inflow acceleration rate during heart ejection, were evaluated as a representation of E/sub MAX/ using Novacor VAD volume and mean arterial pressure measurements from a computer simulation. The maximum VAD inflow acceleration rate during heart systole showed a strong correlation to the E/sub MAX/ regardless the variation of native heart rate, and thus can be used as an E/sub MAX/ index.