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This Article Full Text Full Text (PDF) All Versions of this Article: 290/4/H1474    most recent 00663.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Claessens, T. E. Articles by Segers, P. Search for Related Content PubMed PubMed Citation Articles by Claessens, T. E. Articles by Segers, P.

Nonlinear isochrones in murine left ventricular pressure-volume loops: how well does the time-varying elastance concept hold?

¹Institute of Biomedical Technology, Ghent University, Gent, Belgium; Departments of ²Medicine and ³Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland; ⁴Millar Instruments, Houston, Texas; ⁵Laboratory of Hemodynamics and Cardiovascular Technology, Lausanne, Switzerland; and ⁶Laboratory for Physiology, Institute of Cardiovascular Research-Vrije University, Vrije University Medical Center, Amsterdam, The Netherlands

Submitted 20 June 2005 ; accepted in final form 9 November 2005

tThe linear time-varying elastance theory is frequently used to describe the change in ventricular stiffness during the cardiac cycle. The concept assumes that all isochrones (i.e., curves that connect pressure-volume data occurring at the same time) are linear and have a common volume intercept. Of specific interest is the steepest isochrone, the end-systolic pressure-volume relationship (ESPVR), of which the slope serves as an index for cardiac contractile function. Pressure-volume measurements, achieved with a combined pressure-conductance catheter in the left ventricle of 13 open-chest anesthetized mice, showed a marked curvilinearity of the isochrones. We therefore analyzed the shape of the isochrones by using six regression algorithms (two linear, two quadratic, and two logarithmic, each with a fixed or time-varying intercept) and discussed the consequences for the elastance concept. Our main observations were 1) the volume intercept varies considerably with time; 2) isochrones are equally well described by using quadratic or logarithmic regression; 3) linear regression with a fixed intercept shows poor correlation (R² < 0.75) during isovolumic relaxation and early filling; and 4) logarithmic regression is superior in estimating the fixed volume intercept of the ESPVR. In conclusion, the linear time-varying elastance fails to provide a sufficiently robust model to account for changes in pressure and volume during the cardiac cycle in the mouse ventricle. A new framework accounting for the nonlinear shape of the isochrones needs to be developed.

ventricular function; curvilinear; end-systolic pressure-volume relationship

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