[The vortex cordis is never reversely directed, even in situs inversus and L-loop anomaly]

In 1926, Taussig reported on two instances of complete situs inversus of the heart and stated that "the main anatomical structure and the deep muscle bundles of the ventricles presented the mirror image of the normal, while the direction of the superficial muscle bundles remained unchanged". In an attempt to analyze whether her statement always held true, we examined the myocardial architecture of five specimens of situs inversus totalis. They were all from patients over sixty years of age and were diagnosed by postmortem examination. Every part of the heart and great vessels presented exact mirror images of the normal. However, the external muscle fibers of the ventricles ran clockwise from base to apex toward the center of the vortex, which had a striking resemblance to the normal rather than the mirror image pattern. Peeling off of the external layer revealed that the direction of fibers was first inverted and then changed into an approximate mirror image of the normal architecture within the deeper muscle layers, as illustrated by Taussig. The exception to this tendency was found at the posterior region of the morphologically left ventricle, in which there was no mirror imaging but a normal pattern throughout the depth of the wall. For the purpose of comparison, two hearts of corrected transposition (L-TGA) were examined. Their chambers were inverted but the external fibers followed the same clockwise course seen in the normal heart. Further dissection revealed that there was no mirror imaging of the architecture at any depth of the morphologically left ventricular wall. Thus there were regional differences and similarities in muscular architecture between these two kinds of ventricular inversion. It was concluded that the vortex layer was never reversely directed, even in situs inversus and L-loop anomaly, and that the deep layers within the sinus region of the left ventricle did not present a mirror image to the normal.