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Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance

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 d...

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Autores principales: Garrett, Amy S., Pham, Toan, Loiselle, Denis, Han, June‐Chiew, Taberner, Andrew
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739510/
https://www.ncbi.nlm.nih.gov/pubmed/31512409
http://dx.doi.org/10.14814/phy2.14184
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author Garrett, Amy S.
Pham, Toan
Loiselle, Denis
Han, June‐Chiew
Taberner, Andrew
author_facet Garrett, Amy S.
Pham, Toan
Loiselle, Denis
Han, June‐Chiew
Taberner, Andrew
author_sort Garrett, Amy S.
collection PubMed
description 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.
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spelling pubmed-67395102019-09-14 Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance Garrett, Amy S. Pham, Toan Loiselle, Denis Han, June‐Chiew Taberner, Andrew Physiol Rep Original Research 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. John Wiley and Sons Inc. 2019-09-11 /pmc/articles/PMC6739510/ /pubmed/31512409 http://dx.doi.org/10.14814/phy2.14184 Text en © 2019 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Original Research
Garrett, Amy S.
Pham, Toan
Loiselle, Denis
Han, June‐Chiew
Taberner, Andrew
Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance
title Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance
title_full Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance
title_fullStr Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance
title_full_unstemmed Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance
title_short Mechanical loading of isolated cardiac muscle with a real‐time computed Windkessel model of the vasculature impedance
title_sort mechanical loading of isolated cardiac muscle with a real‐time computed windkessel model of the vasculature impedance
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739510/
https://www.ncbi.nlm.nih.gov/pubmed/31512409
http://dx.doi.org/10.14814/phy2.14184
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