Abstract:The effect of blood hematocrit (HCT) on a noninvasive flow estimation algorithm was examined in a centrifugal implantable rotary blood pump (iRBP) used for ventricular assistance. An average flow estimator, based on three parameters, input electrical power, pump speed, and HCT, was developed. Data were collected in a mock loop under steady flow conditions for a variety of pump operating points and for various HCT levels. Analysis was performed using three-dimensional polynomial surfaces to fit the collected data for each different HCT level. The polynomial coefficients of the surfaces were then analyzed as a function of HCT. Linear correlations between estimated and measured pump flow over a flow range from 1.0 to 7.5 L/min resulted in a slope of 1.024 L/min (R 2 = 0.9805). Early patient data tested against the estimator have shown promising consistency, suggesting that consideration of HCT can improve the accuracy of existing flow estimation algorithms. Key Words: Implantable rotary blood pump-Noninvasive flow estimation-Control strategyLeft ventricular assist device-Hematocrit-Rotary blood pump.

This model represents an important step on the path towards unveiling the complexity of cardiac torsion. It proves to be a practical and versatile tool which could assist clinicians and researchers by providing them with easily-accessible, detailed data on cardiac kinematics for future diagnostic and surgical purposes.

The assessment of Left Ventricular Apex (LVA) kinematics throughout the cardiac cycle could be useful for evaluating cardiac performance and efficiency. We proposed and evaluated in a sheep the use of a real-time 3D magnetic tracking system for the analysis of LVA kinematics. LVA kinematics was assessed using a realtime 3D magnetic tracking system, whose sensor was epicardially glued on the exposed LVA. Two indexes were calculated from the 3-Dimensional apex path traced by the magnetic sensor: the 3D Apex Path Length (3DAPL, length of 3D apex path) and the 3D Apex Path Volume (3DAPV, volume containing 3D apex path). Hemodynamic index of cardiac contractility (LVdP/dt MAX) was derived from Left Ventricular Pressure (LVP) measurement and evaluated against LVA kinematics parameters, at baseline and after acute ischemia, experimentally induced by coronary ligation. Results showed an opposite trend between LV hemodynamics and LVA kinematics: in the ischemic heart an increase of both 3DAPL (+24.5%) and 3DAPV (+151.7%) occurred compared with baseline, while LVdP/dt MAX decreased (-36.9%).