In 1926, the famous American pediatric cardiologist, Dr. Helen B. Taussig, observed that in situsinversus totalis (SIT) main gross anatomical structures and the deep muscle bundles of the ventricles were a mirror image of the normalstructure, while the direction of the superficial muscle bundles remained unchanged (H. B. Taussig, Bull Johns Hopkins Hosp 39: 199–202, 1926). She and we wondered about the implication of this observation for left ventricular (LV) deformation in SIT. We usedmagnetic resonance tagging to obtain information on LV deformation, rotation, and torsion from a series of tagged images in five evenly distributed, parallel, short-axis sections of the heart of nine controlsand eight persons with SIT without other structural (cardiac) defect. In the controls, during ejection, the apex rotated counterclockwise withrespect to the base, when looking from the apex. Furthermore, the base-to-apex gradient in rotation (torsion) was negative and similar at all longitudinal levels of the LV. In SIT hearts, torsion was positivenear the base, indicating mirrored myofiber orientations compared with the normal LV. Contrary to expectations, torsion in the apical regions of SIT LVs was as in normal ones, reflecting a normal internalmyocardial architecture. The transition zone with zero torsion, found between the apex and base, suggests that the heart structure in SIT is essentially different from that in the normal heart. This provides a unique possibility to study regulatory mechanisms for myocardial fiber orientation and mechanical load, which has been dealt with in the companion paper by Kroon et al.
|Journal||American Journal of Physiology : Heart and Circulatory Physiology|
|Publication status||Published - 2008|