Istituto di Fisiologia Clinica     
Ferrari G., Khir A. W., Fresiello L., Di Molfetta A., Kozarski M. Hybrid model analysis of IABP performance as a function of ventricular and circulatory parameters. In: Artificial Organs, vol. 35 (9) pp. 902 - 911. Wiley Periodicals, 2011.
Objectives: to investigate the effects of the intra aortic balloon pump (IABP) on endocardial viability ratio (EVR), Cardiac Output (CO), end systolic (Ves) and end diastolic (Ved) ventricular volumes, total coronary blood flow (TCBF) and ventricular energetics (EW, PVA) under different ventricular (Emax and diastolic stiffness) and circulatory (arterial compliance) parameters. Materials and Methods: We derived from a computational model a hybrid model, which is based on merging computational and hydraulic sub-models. The lumped parameter computational sub-model consists of left and right hearts, systemic, pulmonary and coronary circulations. The hydraulic sub-model includes part of the systemic arterial circulation; essentially a silicon rubber tube representing the aorta, which contains a 40cc IAB. EVR, CO, Ves and Ved, TCBF and ventricular energetics (EW, CME, PVA) were analyzed against the ranges of left ventricular Emax (0.3-0.5-1 mmHg cm-3) and diastolic stiffness Vstiffness (»0.08 and »0.3 mmHg cm-3, obtained by changing diastolic stiffness constant) and systemic arterial compliance (1.8-2.5 cm3 mmHg-1). All experiments were performed comparing the selected variables before and during IABP assistance. Results: Increasing Emaxl from 0.5 to 2 mmHg·cm-3 resulted in IABP assistance producing lower percentage changes in the selected variables. The changes in VS strongly influence both absolute value of EVR and its variations during IABP (71% and 65% for lower and higher arterial compliance, respectively). Ved and Ves changes are rather small but higher for lower Emax and higher Vstiffness. Lower Emax and higher Vstiffness resulted in higher CBF and CO during IABP assistance (~35% and 10%, respectively. Conclusions: The use of this hybrid model allows for testing real devices in realistic, stable and repeatable circulatory conditions. Specifically, the presented results show that IABP performance is dependent at least in part on left ventricular filling, ejection characteristics and arterial compliance. It is possible in this way to simulate patient specific conditions and predict the IABP performance at different values of the circulatory or ventricular parameters. Further work is required to study the conditions for heart recovery modeling, baroreceptor controls and physiological feedbacks.
Subject Intra-aortic balloon pump, cardiovascular modelling, comprehensive model, hybrid model, computational model

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