The effects of pericardial fluid and fibrosis on ventricular defibrillation threshold: A finite element method study

Pericardial effusion and pericardial fibrosis often occur after the implantation of internal defibrillators that use electrodes on the heart surface. The pericardial effusion and fibrosis may increase the defibrillation threshold and thus reduce the lifetime of the implantable defibrillators. But the data from animal experiments regarding the relations between the defibrillation threshold and the pericardial effusion or fibrosis are not conclusive. The purpose of this work is to investigate the effects of the pericardial effusion and fibrosis on defibrillation threshold by calculating defibrillation current density distribution with finite element method (FEM). A sphere model for an isolated dog heart is created and the FEM calculations for the sphere model shows that the pericardial effusion has a nonlinear effect on the defibrillation threshold energy, and the pericardial fibrosis can increase the defibrillation threshold energy by up to 98%. A dog heart model with moderate details in anatomy is also created and the FEM calculations for this model shows that the pericardial effusion has a nonlinear effect on the defibrillation threshold energy, and reduces inter-electrode resistance by at least 44%.