  In the framework of accurate and efficient segregated schemes for 3D cardiac
electromechanics and 0D cardiovascular models, we propose here a novel
numerical approach to address the coupled 3D-0D problem introduced in Part I of
this two-part series of papers. We combine implicit-explicit schemes to solve
the different cardiac models in a multiphysics setting. We properly separate
and manage the different time and space scales related to cardiac
electromechanics and blood circulation. We employ a flexible and scalable
intergrid transfer operator that enables to interpolate Finite Element
functions among different meshes and, possibly, among different Finite Element
spaces. We propose a numerical method to couple the 3D electromechanical model
and the 0D circulation model in a numerically stable manner within a fully
segregated fashion. No adaptations are required through the different phases of
the heartbeat. We also propose a robust algorithm to reconstruct the
stress-free reference configuration. Due to the computational cost associated
with the numerical solution of this inverse problem, the reference
configuration recovery algorithm comes along with a novel projection technique
to precisely recover the unloaded geometry from a coarser representation of the
computational domain. We show the convergence property of our numerical schemes
by performing an accuracy study through grid refinement. To prove the
biophysical accuracy of our computational model, we also address different
scenarios of clinical interest in our numerical simulations by varying preload,
afterload and contractility. Indeed, we simulate physiologically relevant
behaviors and we reproduce meaningful results in the context of cardiac
function.
