Simulation and wave intensity analysis of intra-aortic counterpulsation

Abstract

This work aims at developing a system dynamic model that can simulate various hemodynamic and wave characteristics associated with the counter-pulsation circulation support. A novel hybrid circulation model consisting of a onedimensional (1-D) flow model and a lumped parameter Windkessel model was constructed. High-resolution Roe-splitting was developed for wave capturing and Runge-Kutta method was used for time-stepping this coupled hybrid circulation system. Wave propagation phenomenon in the arteries was successfully simulated. By adjusting the time-varying elastance of the ventricles, the healthy and failed heart conditions can be simulated. Failing heart supported by intra-aortic balloon pump (IABP) was simulated. These simulation results indicate that for 40 ml IABP support, cardiac output was elevated 4.1%. During systolic unloading, IABP deflation generated a backward decompression wave, with a ‘‘sucking’’ effect toward the aortic root, resulting in a reduced left ventricular afterload. During diastolic augmentation, IABP inflation generated a backward compression wave, with a ‘‘pushing’’ effect toward the aortic root to help coronary diastolic perfusion. Wave patterns of counterpulsation can be investigated using wave intensity analysis, which is able to quantitatively assess diastolic augmentation and systolic unloading of IABP counterpulsation based on a strict energy transport theory of wavelet.