Investigation of cardiac and cardio-therapeutical phenomena using a pulsatile circulatory model / Untersuchung kardiologischer und kardiotherapeutischer Phänomene anhand eines pulsatilen Herz/Kreislauf-Modells

Abstract

For many years computer models of the cardiovascular system have existed with which the complex physiological interrelations of regulation processes may be studied. However, one major disadvantage of these models is the simplified modeling of the heart kinematics whereby the short term regulation effects of the heart itself on varying physical strains may only be simulated rudimentarily. The developed pulsatile model emphasizes the detailed description of the systolic wall tension progression subject to the Hill/Frank-Starling mechanisms and the simulation of the cardiac valves. Moreover, to be able to describe long term effects the pulsatile model was coupled to the established cardio vascular model of Guyton. Using the coupled system the influences of impaired valve function and ventricular relaxation disorders on the cardiac output as well as the need for an implementation of a physical strain dependent av-delay in existing pacemaker types were investigated. Both the dynamics and the steady-state values of a subset of variables (pressure, volume, flow) were successfully validated by comparing them to published experimental and clinical recordings.

In Vivo Validation of a Cardiovascular Simulation Model in Pigs

“…Modelling the time-varying elastance as being load-independent might not apply, at least when the cardiac load is changed by a VAD [47]. Due to a lack of other direct comparisons between animal and simulated data, it is not clear whether other approaches to model cardiac activity [13][14][15][16] are superior to our approach.…”

“…Another factor that has a high impact on the simulatory results is the modelling of the vascular system. We chose the three-element Windkessel model [50], as this model has been well-examined and established [9,12,13]. However, there are other approaches [14] that might be favourable, considering certain problems, e.g., the difficult determination of compliance and resulting characteristic impedance, as mentioned above.…”

“…In addition to the different strategies to implement basic physiological conditions, the various models also differ in complexity and focus on specific physiological phenomena. Generally, three different types of models are distinguishable: myocardial activity can be modelled by a time-varying elastance curve [3,[6][7][8][9][10][11][12], a sarcomere model [13][14][15], or isovolumetric contractions [16,17]. In the first case, emphasis is placed on the correct simulation of the starling curve; in the second case, the interaction between sarcomere and ventricular cavity mechanics is addressed; in the third case, the afterload dependency of the heart is stressed.…”