Myocardial Torsion. Jorge C. Trainini

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      Figure 1.45. Radiologic image of the cardiac fulcrum with mammography technique in the bovine heart.

      The cardiac fulcrum is adjacent and anteroinferior to the right trigone, constituting a solid, homogeneous structure to palpation with osseous, chondroid or tendinous histology. It is the site where the right segment and the ascending segment fibers attach, origin and end of the myocardial band. These insertions must be understood as the supporting point of the myocardial band to fulfill its hemodynamic function.

      Regarding the study on this point of attachment which we have termed cardiac fulcrum, it must be considered as an organic structure that supports the band, allowing it to develop the necessary force for the fundamental rotational motions of the left ventricle. (131, 132) We should not forget that the heart pendulates within the thoracic cavity and its points of attachment are the origin and end of the myocardial muscle band, very close to each other at the root of the aorta and of the pulmonary artery. The origin of the band at the cardiac fulcrum is essentially a point of attachment for the right segment forming the band origin and also its end with the ascending segment. This anatomical site finds correspondence with the active motions of the cardiac cycle: left ventricular systole and suction. The site of the cardiac fulcrum in the rope model shown in Figure 1.46 simplifies the understanding of the myocardial band.

      Figure 1.46. Site of the cardiac fulcrum in the myocardial band (rope model). The inset shows (in red) the schematic diagram of the rope model overlapping with the myocardium.

      Conclusion. This anatomical description, both in bovid and human hearts, would put an end to the lack of support of the myocardial band to fulfill its twisting function, as the cardiac fulcrum (Figure 1.47) is the insertion point to achieve the necessary leverage, same as a muscle with its bone insertion. The observation of the tendinous cardiac fulcrum as a meeting point between the origin and end of the myocardial band would confirm its helical configuration. Moreover, by achieving energy dissipation, this nucleus would avoid the twisting motion of the ventricular helix from shifting to the aorta and hampering systolic ejection.