Abstract

To date, the mechanical loads imposed on isolated cardiac muscle tissue in vitro have been oversimplified. Researchers typically applied loads that are time‐invariant, resulting in either isometric and auxotonic contractions, or flat‐topped (isotonic shortening) work‐loops. These contraction types do not fully capture the dynamic response of contracting tissues adapting to a variable load, such as is experienced by ventricular tissue in vivo. In this study, we have successfully developed a loading system that presents a model‐based, time‐varying, continuously updated, load to cardiac tissue preparations. We combined a Windkessel model of vascular fluid impedance together with Laplace's Law and encoded it in a real‐time hardware‐based force‐length control system. Experiments were carried out on isolated rat left ventricular trabeculae; we directly compare the work‐loops arising from this protocol with those of a typical simplified isotonic shortening work‐loop system. We found that, under body conditions, cardiac trabeculae achieved greater mechanical work output against our new loading system, than with the simplified isotonic work‐loop protocol. We further tested whether loading the tissue with a mechanical impedance defined by “diseased” Windkessel model parameters had an effect on the performance of healthy trabeculae. We found that trabecula shortening decreased when applying the set of Windkessel parameters describing the hypertensive condition, and increased in the hypotensive state. Our implementation of a real‐time model of arterial characteristics provides an improved, physiologically derived, instantly calculated load for use in studying isolated cardiac muscle, and is readily applicable to study various disease conditions.

Highlights

  • Cardiac output is determined by the mechanics of the heart, and of the circulation into which it empties

  • Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society

  • We describe the mechanical impedance of the arterial system using a lumped-parameter Windkessel model, as first proposed by Frank (1899) (English translation by Sagawa et al (1990)

Read more

Summary

Introduction

Cardiac output is determined by the mechanics of the heart, and of the circulation into which it empties. The pressure in the left ventricle drives against the impedance of the systemic circulation, which is contributed by the compliance of the large arteries proximal to the systemic circulation, and the resistance of smaller peripheral arteries. These physical characteristics in turn determine the time-course of pressure decay in the aorta during diastole, and the pressure required to be developed in the left ventricle for ejection to occur during the following beat (Sonnenblick and Downing, 1963; Milnor, 1975).

Methods
Results
Conclusion
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.