Longitudinal and Circumferential Strain.
Concerning the shortening, and thickening in the circumferential,
longitudinal, or radial dimensions, it is not addressed what it means or
why this deformation occurs, which is linked to its helical morphology.
Longitudinal strain reflects downward displacement of the AL fibers to
generate the normal ejection fraction on average of 60%.
(Figure 1: 3 DS-AS) In contrast, short-axis shortening
arises from predominantly circumferential fiber deformation, but only a
30% ejection fraction occurs46 (Figure
1: 3 RS-LS) These changes in fiber angulation have implications
because systolic contractile resistance Impaired AL develops when the
ventricle becomes spherical and the AL muscle fibers lose their
obliquity to a more transverse orientation. Longitudinal strain
quantifies ventricular shortening and reflects the action of the DS and
its sequential shortening in the base-apex direction, so ”pull-down”
inferences contradict the helical dynamics of
motion42.(Figure 4: 1A-C, predominance
of vectors towards apical direction and endocardial direction.)
The short-axis shortening of the transverse fibers of the BL and the
transverse shortening produced by subendocardial DS are two factors
explaining why circumferential deformation produces ventricular
compression or cardiac narrowing their contributions cannot be
determined by the overlap within the free wall of the LV, the
interventricular septum does not contain a circumferential envelope, so
its measurement of longitudinal deformation is possible, this can be
measured by recording the excursion of the mitral annulus towards the
apex (MAPSE). Altered longitudinal strain is an early finding in
ventricular dilatation and develops when the conical ventricular shape
becomes spherical, causing the natural oblique fibers to develop a
transverse configuration that disrupts their torsion
capacity47. The functional validity of this concept is
confirmed by the consistent return of cardiac torsion when the spherical
shape of the failing heart is restored to its natural elliptical shape,
as seen after properly performed ventricular restorative surgical
procedures48, 49.