  Knowledge of appropriate local fiber architecture is necessary to simulate
patient-specific electromechanics in the human heart. However, it is not yet
possible to reliably measure in-vivo fiber directions, especially in human
atria. Thus, we present a method which defines the fiber architecture in
arbitrarily shaped atria using image registration and reorientation methods
based on atlas atria with fibers predefined from detailed histological
observations. Thereby, it is possible to generate detailed fiber families in
every new patient-specific geometry in an automated, time-efficient process. We
demonstrate the good performance of the image registration and fiber definition
on ten differently shaped human atria. Additionally, we show that
characteristics of the electrophysiological activation pattern which appear in
the atlas atria also appear in the patients' atria. We arrive at analogous
conclusions for coupled electro-mechano-hemodynamical computations.
