Right Versus Left Ventricular Myofiber Orientation in Various Congenital Heart Diseases Analyzed with X-Ray Phase-Contrast Tomography

BACKGROUND While the systemic right and left ventricles have different functional prognoses, only a limited number of reports have addressed their myocardial architecture. This study analyzed myofiber orientation of human specimens with various congenital heart diseases using X-ray phase-contrast tomography. METHODS Three specimens of each normal heart, ventricular septal defect, right atrial isomerism, left atrial isomerism, and ventricular inversion were examined. In reconstructed images of both ventricles, the center of the free wall was resliced parallel to the myocardial surface. A myofiber helical angle was identified in each slice and plotted from epicardium to endocardium. The plotted curves were compared between both ventricles. RESULTS In all ventricles, the helical angle was changed from left-handed on epicardial slices to right-handed on endocardial slices. Whereas the right ventricle’s helical angle curves showed a plateau with or without a rapid rise on the endocardial side, the left ventricle’s curves had sustained increase with or without a plateau in the middle. The median wall-thickness– scaled helical angle change rates were 53° and 102° in the right and left ventricle, respectively, and their distribution of each specimen was higher in the left ventricle than in the right ventricle. CONCLUSIONS: Ventricular myofiber orientation has a consistent transmural helical transition independently of cardiac morphology and looping. Their transitions can have a plateau and rapid changes permitting the identification of layers within the ventricular wall. The left ventricle has more helical fibers and the right ventricle has more circumferential fibers, which may explain their difference of ventricular performance.