Why Is The Heart Helical?

Introduction: The myocardium is a continuous, integral, longitudinal muscle. When folded, it forms a helix, aligning the ventricles contiguously and interdependently througha septum, allowing for the torsion/detorsion mechanics. This study explores the fundamental twists of the continuous myocardium that allow it to achieve its helical position. Materials and Methods: Eighty-three bovine, human, porcine, and anuran hearts were used. They were subjected to myocardial unfolding. Histology was performed with hematoxylin-eosin staining, Masson’s trichrome technique, and 4-micron sections. Results: The continuous myocardium, which forms a helix, produces three twists along its length. The first is located horizontally in the basal loop, forming the free wall of the right ventricle. The second twist occurs between the left segment and the descending segment. Its location is referenced by the posterior papillary muscle. It is the sum of a 180-degree torque in the linearity of the myocardium, similar to a Möbius strip, together with a sudden twist that directs it downward toward the cardiac apex at a 90-degree angle. The third, located between the descending segment and the ascending segment, is the apical twist, with the anterior papillary muscle as an anatomical reference. This involves a change in the direction of the myocardium: the downward orientation of the myocardium becomes ascending. Conclusions: The three twists that occur in the continuous myocardium constitute a hallmark of the helical heart. They allow the ventricles to be aligned contiguously, forming the septum by directing the descending segment (continuity of the left segment) in parallel and contiguous with the ascending segment, which arises from the continuity of the descending segment when it changes direction at the apex, oriented toward the cardiac base. In this way, the anisotropic properties of its fibers determine that stimulation, when passing between these segments, can produce a helical movement with opposing forces, leading to myocardial torsion-detorsion. Keywords : Continuous myocardium-Helical heart-Cardiac dissection