Blood flow structure and dynamics, and ejection mechanism in the left ventricle: Analysis using echo-dynamography

SummaryUsing our “echo-dynamography”, blood flow structure and flow dynamics during ventricular systole were investigated in 10 normal volunteers. The velocity vector distribution demonstrated blood flow during ejection was laminar along the ventricular septum. The characteristic flow structure was observed in each cardiac phases, early, mid- and late systole and was generated depending on the wall dynamic events such as peristaltic squeezing, hinge-like movement of the mitral ring plane, bellows action of the ventricle and dimensional changes in the funnel shape of the basal part of the ventricle, which were disclosed macroscopically by using the new technology of high speed scanning echo-tomography and microscopically by the strain rate distribution measured by phase tracking method.The pump function was reflected on the changes in the flow structure represented by the flow axis line distribution and the acceleration along the flow axis line. The acceleration of the ejection had three modes, “A”, “B” and “C”, and generated by the wall dynamic events. “A” appeared from the apical to the outflow area along the main flow axis line, “B” along the anterior mitral leaflet and the branched flow axis line, and “C” generated by the high speed vortex behind the mitral valve. The magnitude of the acceleration was estimated quantitatively from the velocity gradient along the flow axis line. Macroscopic and microscopic asynchrony in the myocardial contraction and extension appeared systematically in the local part of the ventricular wall, which was helpful for making the flow structure and for performing the smooth pump function

Non-uniform distribution of the contraction/extension (C–E) in the left ventricular myocardium related to the myocardial function

AbstractObjectiveWe attempted to disclose the microscopic characteristics of the non-uniform distribution of the contraction and extension (C–E) of the left ventricular (LV) myocardium using a new methodology (echo-dynamography).MethodsThe distributions of the “axial strain rate” (aSR) and the intra-mural velocity in the local areas of the free wall including the posterior wall (PW) and interventricular septum (IVS) were microscopically obtained using echo-dynamography with a high accuracy of 821μm in the spatial resolution. The results were shown by the color M-mode echocardiogram or curvilinear graph. Subjects were 10 presumably normal volunteers.Results(1)Both the C–E in the pulsating LV wall showed non-uniformity spatially and time-sequentially.(2)The C–E property was better evaluated by the aSR distribution method rather than the intra-mural velocity distribution method.(3)Two types of non-uniformity of the aSR distribution were observed: i.e. (i) the difference of its (+)SR (contraction: C) or (−)SR (extension: E) was solely the “magnitude”; (ii) the coexistence of both the (+) SR and (−)SR at the same time.(4)The aSR distribution during systole was either “spotted,” or “multi-layered,” or “toned” distribution, whereas “stratified,” “toned,” or “alternating” distributions were observed during diastole.(5)The aSR distribution in the longitudinal section plane was varied in the individual areas of the wall even during the same timing.(6)To the mechanical function of the LV, there was a different behavior between the IVS and PW.ConclusionsThe aSR and its distribution were the major determinants of the C–E property of the LV myocardium. Spatial as well as time-sequential uniformity of either contraction or extension did not exist. The myocardial function changed depending on the assemblage of the aSR distribution, and by the synergistic effect of (+)SR and (−)SR, the non-uniformity itself potentially served to hold the smooth LV mechanical function