Characterization of the normal cardiac myofiber field in goat measured with MR-diffusion tensor imaging

1 Department of Mechanical Engineering and 2 Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven; 3 Department of Experimental In Vivo NMR, Utrecht University, 3508 TC Utrecht; and 4 Department of Biophysics, Maastricht Univesity, Maastricht, 6200 MD The Netherlands Cardiac myofiber orientation is a crucial determinant of the distribution of myocardial wall stress. Myofiber orientation is commonly quantified by helix and transverse angles. Accuracy of reported helix angles is limited. Reported transverse angle data are incomplete. We measured cardiac myofiber orientation postmortem in five healthy goat hearts using magnetic resonance-diffusion tensor imaging. A novel local wall-bound coordinate system was derived from the characteristics of the fiber field. The transmural course of the helix angle corresponded to data reported in literature. The mean midwall transverse angle ranged from 12 ± 4° near the apex to +9.0 ± 4° near the base of the left ventricle, which is in agreement with the course predicted by Rijcken et al. (18) using a uniform load hypothesis. The divergence of the myofiber field was computed, which is a measure for the extent to which wall stress is transmitted through the myofiber alone. It appeared to be