Development of Helical Myofiber Tracts in the Human Fetal Heart: Analysis of Myocardial Fiber Formation in the Left Ventricle From the Late Human Embryonic Period Using Diffusion Tensor Magnetic Resonance Imaging

Figures

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  Figure 1. Three‐dimensional reconstruction and fiber tracts of the fetal hearts. A, Embryonic heart at Carnegie stage (CS) 23: T1‐weighted magnetic resonance imaging on the upper‐middle section (left), 3‐dimensional reconstruction (middle), and fiber tracts are visualized using DSI Studio (right). B, Fetal hearts from the fetus with a crown‐rump length (CRL) of 30 mm (12 WGA) and CRL of 94 mm: fiber tracts are visualized at the ventral and apical views (CRL, 30 mm) and ventral view (CRL, 94 mm). LV indicates left ventricular; and RV, right ventricular.

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  Figure 2. Upper‐middle cross‐sectional view showing the myofiber tracts coded by the helix angle (HA). The concentric gradual changes in the colors indicate a smooth transmural change in HA values (from positive to negative) in all directions in the ventricles. Any prelevel or regional differences are not seen in the samples of the fetus with a CRL (CRL) of 23 mm and in the larger samples in the fetal period. CS indicates Carnegie stage; and WGA, weeks of gestation.

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  Figure 3. Transmural change in the helix angle (HA) on left and right ventricles. HA value against transmural depth in left ventricular wall segments of human fetal hearts from fetuses with a crown‐rump length (CRL) of 23 mm (Carnegie stage [CS] 23) (A) and CRL of 160 mm (20 weeks of gestation) (B).

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  Figure 4. Change in helix angle (HA) value in the 4 areas on the upper‐middle region of the left and right ventricles according to growth. The linear change was detected in the transmural HA value in all hearts except the smaller samples in the embryonic period. Such linear change is interrupted at the posterior wall in the embryonic heart (arrow). CS indicates Carnegie stage; and CRL, crown‐rump length.

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  Figure 5. Transmural difference in helix angle (HA) value between the inside and outside of the ventricular wall according to growth. The transmural difference in HA value (green dots) is calculated as the difference between the maximum positive value inside (red rectangle) and the maximum negative value outside (blue rectangle) the ventricular wall. CRL indicates crown‐rump length.

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  Figure 6. Fractional anisotropy (FA) on ventricular walls according to crown‐rump length (CRL). A, Upper‐middle cross‐sectional view showing the myofiber tracts coded by FA value. B, Box plots of FA values in each voxel of the entire left ventricle. In the box plots, the bars represent the sample range, the boxes represent the second and third quartiles, and the middle line represents the median. The acute change between CRL of 30 and 32 mm (12 and 11 weeks of gestation [WGA]) might be a secondary artifact. It will be worth analyzing more samples to better understand the progression.

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  Figure 7. Propagation angle (PA) on ventricular walls according to crown‐rump length (CRL). Upper‐middle cross‐sectional view showing the myofiber tracts coded by the PA value. WGA indicates weeks of gestation.