Simulation analysis of mechanical properties of the canine heart with bundle branch block based on a 3-D electromechanical model

Asynchronous electrical activation, induced by bundle branch block (BBB), can cause reduced ventricular function. However, effects of BBB on the mechanical function of heart are difficult to assess experimentally. Based on an electromechanical canine heart model developed recently, the mechanical properties of complete LBBB and RBBB were simulated. The geometries and myofibre orientations of ventricles were constructed based on MR scan and diffusion tensor MRI datasets. The electrical activation sequences were simulated by solutions of reaction-diffusion equations and myocardial active forces were used to calculate ventricular wall deformation based on FEM method. The results showed that there is an asynchronous contraction of the septum in BBB during systole, the ejection fraction of left ventricle during LBBB and RBBB is 21.7% and 24.7% respectively, and patients with LBBB may have a more decreased stroke volume and thus are more likely to develop cardiovascular diseases.