Numerical Models of the Cardiovascular System: Interaction Between the Septum and the Left (Right) Ventricular and Atrial Free Wall

Introduction: Mathematical modelling of the cardiovascular system (CVS) can help understand the complex interactions between both ven-tricles and the septum. Variable elastance models are helpful to describe the behaviour of the left (right) ventricular free wall, the atria and the septa in order to reproduce their interactions. The relation between atrial and ventricular mechanical properties and the ECG signal allows the analysis of the effects produced by different ECG delays on haemody-namic parameters. Ventricular interactions play a key role in cardiac mechanics and can be affected by conditions such as symptomatic heart failure secondary to systolic dysfunction or ischaemic dilated cardiomyopathy. Cardiac Resynchronisation Therapy (CRT) is an interventional procedure that may have a potential beneficial effect on the clinical status of selected heart failure patients when acting on the duration of the QRS complex in the ECG signal. Methods: This chapter describes the equations used and implemented in CARDIOSIM©, which is the software simulator of the CVS developed to reproduce the behaviour of the left and right ventricular free wall, left and right atria and septum. The equations are based on variable elastance models which are suitable to reproduce atrial and ventricular interactions Literature data was used in different simulation settings in the context of CRT intervention in a patient with ischaemic dilated cardiomyopathy. Conclusions: A numerical heart model implemented in CARDIOSIM© can reproduce the interaction between the septum, the left (right) ventricle and the left (right) atrium in order to evaluate the effects of CRT. The outcome of the simulations gives a haemodynamic profile in accordance with literature data.