Figure 2: Cartoon Representations of the Myocardial Fiber Architecture

(A) Normal and (B) infarcted left ventricle. α characterizes the inclination of the estimated myocardial fiber orientation of each voxel in relation to the short axis plane (defined by r and t) and tangent plane (defined by t and u). For normal myocardial fiber architecture, the helix angle smoothly changes from the endocardium (red) to mid-myocardium (green) to epicardium (blue). This transmural change is roughly linear and can be characterized by fitting a slope through α plotted against transmural depth yielding the HAT. For infarcted myocardium, the myocardial fiber architecture in the remote region exhibits less right-handed fibers in the endocardium (α > 0) with a “flatter” overall HAT. (C) Representative image quality of the DW images from a single placebo subject before induced MI, baseline MI pre-injection, and post-injection. The DW images were used to reconstruct the diffusion tensor and subsequently used to derive HA. The white arrow points to the center of the scar. α = helix angle; DW = diffusion-weighted; HA = helix angle; HAT = helix angle transmurality.