Session P32.7

Investigation of Mechanical Cardiorespiratory Interactions through Combined Structural and Functional Modelling

M Guerrisi*, I Vannucci, N Toschi

Universita' Tor Vergata
Roma, Italy

Heart chamber volume and pressure fluctuations are significantly influenced by respiration, which elicits control on all cardiovascular phenomena thorough interdependent mechanical and neural pathways. Ventricular interaction is one of the principal mechanisms through which this control is effected, as well as a key mediator of most pathological consequences of heart function impairment.
In order to characterise the role of ventricular interaction in respiratory control of cardiac and vascular haemodynamic, a lumped-parameter model of the entire circulatory system was developed which accounts explicitly for every compartment of systemic and pulmonary circulation as well as nonlinear behaviour of aortic and peripheral circulation. Further, ventricles and septum are described as portions of interactions ellipsoid shells of non-uniform wall thickness, and chamber configuration is derived as a function of pressure gradients by combining shell element equilibrium equations at the sulcus. Ventricular interaction is characterized by calculating coupling coefficients in left/right/intrathoracic pressure and left/right volume space, which are incorporated in the circulation model. The combined model attains physiological values of all compartmental variables across a wide range of cardiac output.
Inclusion of ventricular interdependence significantly affects the structural response of the model to respiration, where the model displays a greater tolerance to intrathoracic pressure changes when ventricular interdependence is incorporated. Further, explicit description of mechanical interaction between heart chambers is mandatory to explain the initial response of ventricular volume changes and the decrement of the left ventricular volume following the onset of inspiration. The relative timing of cardiac cycle and respiration phases significantly affect the cardiac time intervals and volumes, influencing not only the entity, but also the direction of change.
Translation of a detailed mechanical heart chamber description into coupling coefficients matrices yields seamless integration into a functional model, allowing accurate characterization of mechanical ventricular interplay in a haemodynamic context.

(Abstract Control Number: 208)