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TECHNICAL PAPERS

Determinants of Left Ventricular Shape Change During Filling

[+] Author and Article Information
Jeffrey W. Holmes

Department of Biomedical Engineering, Columbia University, New York, NY 10027

J Biomech Eng 126(1), 98-103 (Mar 09, 2004) (6 pages) doi:10.1115/1.1645527 History: Received June 19, 2003; Revised October 09, 2003; Online March 09, 2004
Copyright © 2004 by ASME
Topics: Fibers , Shapes , Stiffness
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References

Figures

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Mean left ventricular pressure (LVP, open circles), volume (LVV, solid circles), shape (solid triangles), and eccentricity (open triangles) curves in eight sham-operated control rats. Large solid circles on pressure tracing indicate (from left) end diastole, beginning of ejection, end of ejection, and beginning of filling.
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Left ventricular shape/volume relationships. (a) Mean data from eight rats demonstrate sphericalization (increasing shape) of the left ventricle during filling (solid circles) and ellipticalization during ejection. (b) Plotting eccentricity, a different measure of shape, against normalized volume for comparison with canine data from Rankin 1980 2 reveals that behavior of rat (circles) and dog (triangles) ventricles is similar, with the rat LV more spherical at all volumes.
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Model simulations of the effect of global chamber compliance on shape change. (a) Mean experimental (closed symbols) and model pressure-volume behavior (open symbols) at 3 different values of the isotropic exponential material constant b1=b2=b3(C=0.5 for all simulations). (b) Corresponding mean experimental and model shape/volume curves. (c) Model behavior across a larger range of material constants. A threefold change in the material constant produced shape change/volume change ratios (ΔSV, open triangles) that covered a range similar to the 95% confidence interval of the experimental data (closed triangles), while normalized ratios (ΔS/(ΔV/EDV), open circles) remained constant and slightly outside the experimental range (closed circles) for all simulations.
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Model simulations of the effect of fiber stiffness and orientations on shape change. (a) Mean experimental (closed symbols) and model pressure-volume behavior (open symbols) at three different ratios of the material constants b1/b2; global stiffness was maintained by decreasing C as b1 increased. (b) Corresponding mean experimental and model shape/volume curves. Increasing fiber stiffness decreases sphericalization during filling. (c) Model behavior across a larger range of material constants. The model covers the 95% confidence interval of the experimental normalized shape change ratios (ΔS/(ΔV/EDV), solid circles) with a four-fold variation in b1/b2 for a symmetric fiber distribution (open circles). With a 10 deg shift in the fiber distribution a 15-fold change in the b1/b2 ratio is required to simulate the same range of shape changes (open triangles).

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