The architecture of the left ventricular myocytes relative to left ventricular systolic function

Abstract

Objective: Mural thickening, combined with longitudinal and circumferential shortening, and apical along with basal twisting are critical components of the left ventricular systolic deformation that contribute to ventricular ejection. It is axiomatic that the spatial alignment of the actively contracting aggregates of myocytes must play a major role in the resulting ventricular deformation. The need to conserve functional global myocytic architecture, therefore, is an important aspect of the surgical manoeuvres affecting ventricular mass and geometry. To investigate the influence of the global alignment of the myocytes on ventricular contraction, we used a mathematical model simulating the large deformations produced by systolic contraction of the left ventricle of a human heart. Methods: The alignment and meshing of the myocytes within their supporting fibrous matrix cause mechanical anisotropy, which was included in the mathematical model in the form of a unit vector field, constructed from the measured trajectories of aggregated myocytes in an autopsied human heart. The relationship between ventricular structure and ventricular dynamics was assessed by analysing the influence of systematic deviations of the orientation of the myocytes from their original alignment, in longitudinal as well as radial directions, on the distribution of stress and strain within the myocardium, as well as on the ejection fraction. In addition, simplified idealised geometries were used to investigate the influence of the overall geometrical modifications.Results: Left ventricular function proved to be robust with respect to small-to-moderate rotational variations in myocytic alignment, up to 148, a finding which we attribute to an equalising effect of the non-uniform anisotropic pattern found in a real heart involving substantial local irregularities in the architecture of the aggregated myocytes. Severe deterioration of function occurred only when deviations in alignment exceeded 308. Conclusions: Our findings substantiate the concept of the myocardial walls representing a continuous three-dimensional meshwork, with the absence of any intermediate structures such as discrete bands or tracts extending over the ventricles, which could be destroyed surgically, thereby adversely affecting systolic function. With appropriate indications, they also support the validity of the surgical procedures performed to reduce ventricular radius and therefore to reduce mural stress. #

Distinct Aspects of Left Ventricular Mechanical Function Are Differentially Associated With Cardiovascular Outcomes and All‐Cause Mortality in the Community

“…Our study extends previous work by investigating LV strains in different planes and concurrently examining their association with distinct CVD outcomes and mortality. Alterations in different strains reflect the integrity and function of myofibers lying in a given orientation, based on location with respect to the inner‐ versus outermost layers of LV 30. Given their location‐dependent susceptibility to various cardiac stressors, myofibers are likely to be variably affected by accumulating risk for different CVD events.…”

“…Alterations in different strains reflect the integrity and function of myofibers lying in a given orientation, based on location with respect to the inner-versus outermost layers of LV. 30 Given their location-dependent susceptibility to various cardiac stressors, myofibers are likely to be variably affected by accumulating risk for different CVD events. Noninvasive measures with the ability to reflect this variation may provide important detailed prognostic information regarding individuals at risk of CVD.…”

Evaluation of left ventricular torsion in children with hypertrophic cardiomyopathy

“…Owing to the fact that the radius of rotation of the subepicardium is greater than that of the subendocardium, the subepicardium produces a greater torque than the subendocardium. [21][22][23] Owing to the heterogeneous patient groups during childhood that demonstrate left ventricular hypertrophy, we focused on children with idiopathic hypertrophic cardiomyopathy. The reported incidence for idiopathic hypertrophic cardiomyopathy in childhood is rare, with about 3.6 per 1 million children.…”

Early Recovery of Left Ventricular Function After Revascularization in Acute Coronary Syndrome

“…The most pronounced findings in our patients were those of the delta increase in LV global and regional SR. While myocardial strain reflects systolic function, its rate represents the velocity of strain changes, thus, in a way, reproducing what older techniques showed [20]. However, the unique advantage of speckle tracking technology is its ability to assess individual segment function as well as regional function.…”

“…These findings are supported by the complex myocardial fiber architecture the LV basal region has, with most of it being circumferential while its subendocardial layer remains longitudinally orientated, compared with the apex which is mainly formed by longitudinal fibers [21]. In addition, the multiple septal branches, diagonals, and marginals do contribute to the basal LV region with a significant degree of blood supply compared to the apex, which is vascularized mainly by the peripheral small branches of the LAD and the RCA [20]. We believe that this study is the first to report such an impact of the location of the arterial culprit lesion on regional LV function recovery after PCI.…”