  Since myocardial fibers drive the electric signal propagation throughout the
myocardium, accurately modeling their arrangement is essential for simulating
heart electrophysiology (EP). Rule-Based-Methods (RBMs) represent a commonly
used strategy to include cardiac fibers in computational models. A particular
class of such methods is known as Laplace-Dirichlet-Rule-Based-Methods (LDRBMs)
since they rely on the solution of Laplace problems. In this work we provide a
unified framework, based on LDRBMs, for generating full heart muscle fibers.
First, we review existing ventricular LDRBMs providing a communal mathematical
description and introducing also some modeling improvements with respect to the
existing literature. We then carry out a systematic comparison of LDRBMs based
on meaningful biomarkers produced by numerical EP simulations. Next we propose,
for the first time, a LDRBM to be used for generating atrial fibers. The new
method, tested both on idealized and realistic atrial models, can be applied to
any arbitrary geometries. Finally, we present numerical results obtained in a
realistic whole heart where fibers are included for all the four chambers using
the discussed LDRBMs.
