Model-based Prediction of a Percutaneous Ventricular Assist Device Performance § Yih-Choung Yu 1 , Marwan A Simaan 2 , Nicholas V. Zorn 3 , and Simon Mushi 1 1 Department of Electrical and Computer Engineering, Lafayette College, Easton, PA 18042 USA 2 Department of Electrical Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA 3 Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA 02420, USA § This work was partially supported by NSF Grants BE-0420848 and ECS-0300097 Abstract – A percutaneous ventricular assist system is an external heart assist device that bypasses blood from the left atrium and returns it to the femoral artery to support patients who suffer from acute heart failure. The system consists of a centrifugal blood pump, an atrial drainage cannula, and various sizes of arterial perfusion cannula. Because the device allows cardiologists the freedom choosing the arterial cannula based on a patient’s body size, it is extremely difficult but important to predict the level of support the device can provide to the patient before the devise is up and running. In this paper, the TandemHeart pVAD (Cardiacassist Inc. Pittsburgh, PA) is modeled as a nonlinear electric circuit, including a speed dependent voltage source and current dependent resistors to predict the performance of the system by specifying pump speed, mean arterial pressure (MAP), and mean left atrial pressure (LAP). The model structure is developed based upon the pipeline theory while the model parameters are identified by least-squares fit of the model to the experimental data. The flow rate is predicted by solving a quadratic equation while coefficients in the equation are scaled, depending on the arterial cannula configurations. The model can predict the flow rates accurately with error indices of all test conditions less than 6%, comparing the predicted flow from the model with the experimental data. I. Introduction A left Ventricular Assist Device (LVAD) is a controlled mechanical pump which is surgically implanted with the patient’s heart to assist the left ventricle in pumping oxygen-rich blood into the patient’s circulatory system [1-5]. A percutaneous left heart assist system, including a transseptal cannula, a blood pump, and a femoral arterial cannula, is a device that bypasses blood from left atrium to femoral artery through a blood pump [6,7]. The transseptal cannula, inserted from femoral vein by way of right atrium then into left atrium through the atrial septum, drains blood from left atrium into a blood pump. The blood pump then returns blood into patient’s femoral artery through an arterial cannula. The advantage of this type of ventricular support is that the whole procedure can be accomplished in a cardiac catheterization laboratory within a short period of time without a major open-heart surgery. Thus, it is beneficial to patients with emergency heart failure. The use of this system requires selecting an appropriate size of arterial cannula to maximize the blood flow rate, and thus the cardiac support, provided by the system, while maintaining certain amount of distal flow through the patient's leg to reduce the risk of distal leg ischemia. Since different sizes of arterial cannulae produce different fluid resistances in the assist circulation loop, this would cause a difference in the assist blood flow rate at the same MAP, LAP, and pump speed conditions. Determining the system performance based on the selection of arterial cannula usually relies on bench top experiments, which is time consuming. If a computer model were available for the evaluation, this would save the time requirement for bench testing. The computer model could also be a tool for cardiologists to choose an appropriate size of arterial cannula for patients. Cannula in the left atrium Standard extra- corporeal blood circuit tubing Commercially available femoral aterial cannulae Standard Y-adapter TandemHeart pVAD Holster TandemHeart pVAD Cannula in the left atrium Standard extra- corporeal blood circuit tubing Commercially available femoral aterial cannulae Standard Y-adapter TandemHeart pVAD Holster TandemHeart pVAD Figure 1. Anatomical fitting of the TandemHeart pVAD 2005 American Control Conference June 8-10, 2005. Portland, OR, USA 0-7803-9098-9/05/$25.00 ©2005 AACC FrA13.5 3835