[Dynamics of coronary blood flow in the presence of aortic valve disease].
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Aortic Valve↗
Biomedical subjects
D Zinemanas
Publications and source records attributed to D Zinemanas.
Integration of structure, function and mass transport in the myocardium.
A left ventricular (LV) model that integrates muscle mechanics, coronary flow, and fluid transport, and accounts for the three-phase (fiber-blood-interstitium) myocardial structure and composition, is used to study the interactions between the mechanics, coronary flow and fluid and mass transport in the myocardium. Theoretical simulations elucidate the effects of ventricular load, coronary perfusion pressure, and fluid and mass transport on ventricular performance and coronary dynamics. The analysis yields a direct relation between cardiac function and structure to cardiac mechanics, coronary flow, and intramyocardial fluid (and mass) transport, and allows to study the interactions between coronary flow, ventricular and myocardial mechanics and intramyocardial fluid shifts.
Animals↗
An integrated model of LV muscle mechanics, coronary flow, and fluid and mass transport.
An integrated left ventricular (LV) model that accounts for the three-phase (fiber-blood-interstitium) myocardial structure and composition is used to study the interactions among myocardial mechanics, coronary flow, and fluid and mass transport. Effects of ventricular load, coronary perfusion pressure, and fluid and mass transport on ventricular performance and coronary dynamics are studied here. In agreement with experimental observations, the analysis shows that 1) coronary flow impediment is not significantly affected by changes in the afterload and preload at constant coronary perfusion pressures, 2) an increase in coronary perfusion pressure increases the intramyocardial pressure (IMP) as well as the mean flow and oscillatory flow amplitude, 3) contractility has a direct effect on IMP and coronary flow impediment, and 4) changes in blood osmolarity and lymphatic outflow, which may cause myocardial edema, affect both ventricular mechanics and coronary flow. Clearly, accounting for fluid and mass transport allows to study the interactions among coronary flow, ventricular and myocardial mechanics, and intramyocardial fluid shifts.
Animals↗
Intramyocardial fluid transport effects on coronary flow and left ventricular mechanics.
An integrated left ventricular (LV) model is used to solve, simultaneously and interactively, the LV mechanics, the coronary blood flow and capillary and interstitial fluid and mass transport, and to analyze the LV behavior under normal as well as pathological conditions. Accounting for the interstitial fluid mass balance in a LV flow-mechanical model allows to determine the LV wall volume in terms of the prevailing mechanical and flow conditions; it allows to uniquely define the flow-mechanical relationship and study pathologies, such as myocardial edema, which are directly related to changes in the myocardial fluid transport and content.
Biological Transport↗
A fluid-mechanical model of deformation during embryo exogastrulation.
Embryo deformation during gastrulation is simulated using a fluid-mechanical approach. The possibility that the deformation is governed by the forces originated at the embryo surface rather than by pulling by filopodia is considered. The slow viscous flow and the deformation during in vitro exogastrulation is solved using a boundary integral equation formulation. The results show a distinct anisotropic distribution of meridional and circumferential tensions, which are capable of producing the dynamics and shape of the archenteron development. This anisotropy suggests the existence of a specific biochemical activity at particular surface regions prior to and during the gastrulation process. The mechanical model can serve as a tool to help discriminate between the possible suggested mechanisms.
Biomechanical Phenomena↗
Surface viscoelastic effects in cell cleavage.
The effect of passive surface traction on the cleavage of cells is incorporated in the cytokinesis hydrodynamic model of Zinemanas and Nir [Biomechanics of cell Division, pp. 281-305, Plenum Press, New York (1987)]. Different rheological behaviours were examined to model the surface tensions which arise due to the passive deformation of the cortex: a Mooney-Rivlin material, an STZC material and a viscoelastic material. The calculations show that passive surface tensions may play a significant role in determining the local surface deformations as well as in the modulation of the surface forces. Varying the rheological model has limited effect on the overall deformations. The latter appear to be affected mostly by contractile filament interactions.
Cell Division↗
Effects of myocardial contraction on coronary blood flow: an integrated model.
The effects of myocardial contraction on the coronary flow are studied by means of an integrated structural model of left ventricular (LV) mechanics, coronary flow, and fluid and mass transport. This model relates global LV performance, and in particular coronary flow dynamics, to myocardial composition and structure and contractile sarcomere activity. Extravascular pressure is identified with hydrostatic tissue pressure, i.e., intramyocardial pressure (IMP), and is determined by the dynamics of myocardial contraction and fluid transport. Consistent with available experimental data, changes in myocardial function and contractile state are simulated by changing the sarcomere contractile properties or changing the LV loading conditions. The model's predictions are successfully compared with a wide range of experimental studies; all but one were performed at a constant coronary perfusion pressure and maximal vasodilation. The results indicate a dominant effect of the myocardial contractile state on coronary flow and a dissociation between coronary compression and LV cavity pressure (LVP) when the pressure is controlled by load changes. However, when active sarcomere contraction is regionally impaired by lidocaine, LVP plays an important role in the coronary flow characteristics. The model adequately predicts observations on the effect of cardiac contraction on systolic and diastolic coronary flows, as well as the role of LVP at different loading and contractile conditions. The analysis supports the hypothesis that coronary compression, as mediated through IMP, is independent of LV loading conditions and depends on myocardial contractility and coronary perfusion pressure.
Biomechanical Phenomena↗