A modular computational circulatory model applicable to VAD testing and training

Abstract

Aim of this work was to develop a modular computational model able to interact with ventricular assist devices (VAD) for research and educational applications. The lumped parameter model consists of five functional modules (left and right ventricles, systemic, pulmonary, and coronary circulation) that are easily replaceable if necessary. The possibility of interacting with VADs is achieved via interfaces acting as impedance transformers. This last feature was tested using an electrical VAD model. Tests were aimed at demonstrating the possibilities and verifying the behavior of interfaces when testing VADs connected in different ways to the circulatory system. For these reasons, experiments were performed in a purely numerical mode, simulating a caval occlusion, and with the model interfaced to an external left-VAD (LVAD) in two different ways: with atrioaortic and ventriculoaortic connection. The caval occlusion caused the leftward shift of the LV p-v loop, along with the drop in arterial and ventricular pressures. A narrower LV p-v loop and cardiac output and aortic pressure rise were the main effects of atrioaortic assistance. A wider LV p-v loop and a ventricular average volume drop were the main effects of ventricular-aortic assistance. Results coincided with clinical and experimental data attainable in the literature. The model will be a component of a hydronumerical model designed to be connected to different types of VADs. It will be completed with autonomic features, including the baroreflex and a more detailed coronary circulation model.

Hemodynamic Effects of Ventricular Assist Device Implantation on Norwood, Glenn, and Fontan Circulation: A Simulation Study

“…A previously developed lumped parameter model of the cardiovascular system (16,18,19) was adapted to this specific study (Fig. 1).…”

“…The model is implemented in Labview 7.1 (National Instruments, Austin, TX, USA), and equations are solved by Euler's method (16,18,19). The model is implemented in Labview 7.1 (National Instruments, Austin, TX, USA), and equations are solved by Euler's method (16,18,19).…”

“…For each section of the numerical model, the input flow is transmitted from the previous block, while the output flow and the generated pressure are calculated and transmitted to the next block. The model is implemented in Labview 7.1 (National Instruments, Austin, TX, USA), and equations are solved by Euler's method (16,18,19). Table 1 shows the parameter default values, with the exception of R_f, Z_bt, and R_asd that are calculated for each patient.…”

“…From systemic arterial pressure waveforms, it was possible to evaluate the time decay that is the combination between resistances and compliances. From these time decay constants, it was possible to estimate the total arterial systemic compliance (16,18,19,25). Starting from the default pulmonary arterial compliance (Cap), the compliance value was decreased empirically to reach the measured systolic pulmonary arterial pressure.…”

Effects of Intra‐Aortic Balloon Pump Timing on Baroreflex Activities in a Closed‐Loop Cardiovascular Hybrid Model

“…IABP modeling can be performed by connecting the IABP to a circulatory hydraulic model (20)(21)(22) or connecting a computational circulatory model to a computational model of the balloon itself (23). In the present work, we advance the hybrid model of the cardiovascular system (9), by including a specific computational representation for baroreflex, and examine its activity in connection to the IABP.…”