Ejection Phase.
During this phase, the circumferential fibers of the BL accompany the AL during its shortening, producing a force perpetuating the continuity of the narrowing during ejection. This will keep the base narrow, counteracting the vectorial forces generated in opposite directions by the DS and AS in movements. of torsion and untorsion of the LV27 (Figure 3: 1A, B, C) at the moment of ejecting and sucking the blood. (Figure 2)
At this moment, the key piece is the entry into contraction of the DS, its shortening moving the base towards the apex of the LV, turning the base clockwise while the apex rotates counterclockwise due to the torque of torsion of the longest lever radius of the AS. (Figure 3: 1B) The mechanical phenomenon of shortening the LV and consequently ejecting blood is provided by the shortening of the DS, although the subepicardial AS is adjacent to it, reports of longitudinal strain at the level of the AS interventricular septum located in both segments of the AL show a positive wave deflection showing its elongation not it’s shortening, the longitudinal strain of the subendocardial DS shows a negative wave deflection denoting its shortening during the ejection phase28. This superimposition of segments in the interventricular septum was documented as an interseptal hyperechoic line delimiting both segments21 and is demonstrated in great detail in the anatomical correlations to the echocardiogram7 (Figure 2 panel 4-3: 3) and tractography8. This difference in directions in the septum can capture opposite shortenings in the longitudinal strain. This activation and deformation of the sequential fiber also coincides with the findings of experimental studies by sonomicrometry reported by various authors19,20,27(Figure 3) where it is evident how there is a shortening of the subendocardium (DS) moments before the ejection phase with a maximum shortening before the traditional isovolumetric relaxation phase, the maximum shortening of the subepicardial AS is recorded once the rapid filling has begun, demonstrating that there is a sequential mechanical activity which follows the segments of the helical pattern (Figure 3: 1-2) , itself the apical short-axis strain velocity vectors demonstrate a radial inward direction of the cavity throughout the endocardium formed by the DS (Figure 2: 1A-B) , in an apical window the strain velocity vectors show an inward motion of the LV cavity of right, left, and apex during early ejection, as ejection period temporally progresses downward motion persists (displacement of base toward apex) during late ejection and now shows leftward directional shift in basal portion of the septum by rotation clockwise by the start of shortening of the AS that will give way to the first diastolic phase (Figure 4: 1A, B, C).
The increased tension in the DS explains its ability to cause shortening and clockwise twisting of the base of the heart, but the simultaneous counterclockwise apical twisting is due to AS torsion (Figure 4: 1 A-C transition of apical vectors in opposite directions) , (Figure 2 B) . Contracting together with a greater radius of curvature. This interaction is responsible for systolic torsion, and recent electrophysiological studies denote a radial transmural activation in the middle third of the interventricular septum,17 explaining this phenomenon by coactivation of the DS and AS simultaneously (Figure 3) . The AS shortens during co-contraction to compress the cavity, but its effect by raising the base of the ventricles is counteracted by the dominance of the SD contraction, which, as we have seen, already contributes a greater percentage to the ventricular mass17, 29.