Cardiac structure discontinuities revealed by ex-vivo microstructural characterization. A focus on the basal inferoseptal left ventricle region

Figures

• 

  Fig. 1. Summary of the tractography processing for delimiting and measuring the aggregate cardiomyocytes bundles located at the RVIP and also called singularity. (Left) A 3D rendering of streamlines filtered with preferential orientation. B Tractograms generation with different FA stopping thresholds and maximum angles. (Right) C Conversion of tractogram into structure delineation using track density imaging and intensity-base thresholding. D Schematics of the heart in long and short axes with all distances measurements and locations

• 

  Fig. 2. Workflow of the EP modelling study. A 3D rendering view of the sample #H1 with the superimpose region of interest used in the EP modeling. B Transverse view with electrode positions and experimental cFA maps that encode the x–y–z coordinates of the aggregate cardiomyocytes orientation. A white dashed contour highlights the identified aggregate cardiomyocytes bundles. C 3D rendering displaying the corresponding meshes and electrode positions. D Usual rule-based fiber configuration used as control in our studies. E Aggregate cardiomyocytes orientation derived from experimental DTI measurement. F Aggregate cardiomyocytes orientation derived from experimental DTI measurement plus a low conductivity interface at the border of identified aggregate cardiomyocytes bundles. G Activation time maps and unipolar signals and pseudo ECGs are computed as outputs of the computational model

• 

  Fig. 3. Visualization in ex-vivo sheep heart of the basal inferoseptal (BIS) left ventricular myocardium using anatomical images and diffusion tensor maps. (Left) A 3D rendering view of the sample #S4 displaying the whole heart (A), after slicing at the base level (B), with a blue cube showing the location of the inferior RVIP (C). (Right) Large views (D) and zoom views (E) of the anatomical images are shown with orthogonal views. FA maps (F). The cFA maps (G) encode the x–y–z coordinates of the aggregate cardiomyocytes direction derived from the DW images using a color code. Streamlines with the color-coding of the cFA (H)

• 

  Fig. 4. Comparison across ex-vivo sheep hearts (N = 5) of the aggregate cardiomyocytes orientation in the BIS left ventricular myocardium in SA view using anatomical and diffusion tensor images. The legend of the metrics of Fig. 3 applies

• 

  Fig. 5. Visualization of the BIS left ventricular myocardium using microCT images and structure tensor derived maps in ex-vivo sheep heart. (Right) A 3D rendering view of the sample #S6 displays the whole heart (A), after slicing at the base with a blue dotted cube showing the ROI in the inferior RVIP (B). Anatomical images (C, D). cFA map (E) and tractography map (F). Circumferential fibers (green arrow); aggregate cardiomyocytes bundles with base to apex fiber orientation (yellow arrows)

• 

  Fig. 6. Histological examination of the basal inferoseptal (BIS) left ventricular myocardium. Histological slice (A) stained with Masson’s trichrome and corresponding anatomical image (B) and cFA maps (C) in the basal inferoseptal (BIS) left ventricular myocardium. Anatomical landmarks such as vessels having a black contrast are indicated with yellow asterisks. The red arrow and red asterisk indicate the location of the region depicting a triangular shape. Panels D–F show an enlarged view of the previous panels. Zoomed rectangle regions (G–L) are indicated and are located either inside the region (G), outside (H, I) or at the junction (J–L). The blue and gray arrows indicate cardiomyocytes in transverse and longitudinal direction respectively. The dash black lines indicate roughly the location of discontinuities in myocyte orientation

• 

  Fig. 7. Comparison across ex-vivo human hearts (N = 5) of the aggregate cardiomyocytes orientation in the BIS left ventricular myocardium in SA view using anatomical and diffusion tensor images. Right panel: sample #H1; Left Panel: samples #H2-5. The legend of the metrics of Fig. 3 applies. Black arrows indicate the "fiber" bundle in the RVIP. Red arrow indicates myocardial scar

• 

  Fig. 8. Comparison across ex-vivo human hearts (N = 5) of the aggregate cardiomyocytes orientation in the BIS left ventricular myocardium in LA view. The legend of the metrics of Fig. 3 applies

• 

  Fig. 9. Normalized histograms of FA for sheep (A) and human (B). The lines represent the distribution of FA in the whole heart (red) and the distribution of FA in the singularity (blue). Dashes lines indicated the average value

• 

  Fig. 10. Activation time maps (left) and difference in activation time maps (right) for the different cases considered in our study. Usual case with rule-based fiber orientation (1st column). Cases incorporating aggregate cardiomyocytes orientation derived from experimental DTI measurement (2nd column) and with the addition of a non-conducting interface at the border of the identified region (3rd column). The activation was initiated by surface pacing as indicated by the black arrow for three different locations