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Contractility and Pump Function of In Vivo Left Ventricle and Its Coupling with Arterial Load: Testing the Assumptions

  • Kiichi Sagawa
  • David A. Kass
  • Seiryo Sugiura
  • Daniel Burkhoff
  • Joe Alexander

Summary

In the studies reviewed, we tested the assumptions inherent in applying the ventricular and vascular elastance concepts to in vivo physiology. The greatest difference between in vivo and isolated heart data appeared to be in the frequently nonlinear shape of the end-systolic pressure-volume relationship (ESPVR). This suggests that linear model parameters may be of only limited value for predictive or modeling purposes. Extreme changes in ejection history in isolated hearts revealed an important positive (as well as negative) influence of ejection; however, in vivo where afterload alterations and ejection fraction changes are likely to be much less marked, the relative impact of these factors remains unclear. Finally, while substantial differences exist between real arterial and 3-element Windkessel model impedances, when they are loaded on a simple elastance model of ventricular contraction, we predicted good agreement on many important hemodynamic coupling variables. Furthermore, the effective arterial elastance Ea appeared to be a reasonable representation of in vivo aortic impedance, and thus may be a useful afterload parameter to be coupled with end-systolic elastance(Ees).

Modifications of the coupling equations derived previously for stroke work and myocardial efficiency will likely need to be made to reflect the nonlinear ESPVR. However, as we noted, this may not substantially alter several previously proposed principles and conclusions based on linear models.

Keywords

Mean Arterial Pressure Stroke Work Contractile State Myocardial Efficiency Inferior Vena Caval Occlusion 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Tokyo 1989

Authors and Affiliations

  • Kiichi Sagawa
  • David A. Kass
  • Seiryo Sugiura
  • Daniel Burkhoff
  • Joe Alexander
    • 1
  1. 1.Department of Biomedical Engineering, School of MedicineThe Johns Hopkins UniversityBaltimoreUSA

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