Laminar fiber architecture and three-dimensional systolic mechanics in canine ventricular myocardium

Publisher Website
Google Scholar
Abstract
Previous studies suggest that the laminar architecture of left ventricular myocardium may be critical for normal ventricular mechanics. However, systolic three-dimensional deformation of the laminae has never been measured. Therefore, end-systolic finite strains relative to end diastole, from biplane radiography of transmural markers near the apex and base of the anesthetized open-chest canine anterior left ventricular free wall (n = 6), were referred to three-dimensional laminar microstructural axes reconstructed from histology. Whereas fiber shortening was uniform [−0.07 ± 0.04 (SD)], radial wall thickening increased from base (0.10 ± 0.09) to apex (0.14 ± 0.13). Extension of the laminae transverse to the muscle fibers also increased from base (0.08 ± 0.07) to apex (0.11 ± 0.08), and interlaminar shear changed sign [0.05 ± 0.07 (base) and −0.07 ± 0.09 (apex)], reflecting variations in laminar architecture. Nevertheless, the apex and base were similar in that at each site laminar extension and shear contributed ∼60 and 40%, respectively, of mean transmural thickening. Kinematic considerations suggest that these dual wall-thickening mechanisms may have distinct ultrastructural origins.