Models of cardiac muscle contraction and relaxation.

Format:

Book

Thesis/Dissertation

Author/Creator:

Palladino, Joseph Leonard.

Contributor:

Noordergraaf, Abraham, advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Computer science.

Biophysics.

Biomedical engineering.

0541.

0786.

0984.

Penn dissertations--Bioengineering.

Bioengineering--Penn dissertations.

Local Subjects:

Penn dissertations--Bioengineering.

Bioengineering--Penn dissertations.

0541.

0786.

0984.

Physical Description:

290 pages

Contained In:

Dissertation Abstracts International 51-08B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

The goal of this dissertation is to develop a comprehensive, quantitative description of cardiac muscle contraction and relaxation. A distributed muscle model based on fundamental principles and experimental observations, and possessing anatomic significance, is evolved to achieve this goal from two simpler lumped models: the time-varying compliance and energy-exchange descriptions. The range of validity of each model is determined by comparison with well-established muscle experiments in the literature, i.e. isometric, isotonic, quick release and stretch and load clamp.

A single time-varying compliance is shown able to describe slow contractile events, i.e. isometric and isotonic contractions. Applied to an ejecting ventricle, it describes isovolumic and ejecting ventricular contractions and demonstrates sensitivity to preload (Frank-Starling) and afterload. This model fails in describing rapid transient contractile phenomena, i.e. the effect of quick changes in muscle length or load.

The time-varying compliance concept was broadened whereby muscle compliance is dictated by the continuous exchange of energy between muscle and its environment, denoted the energy-exchange model. Energy is distributed between biochemical and potential energy, mechanical work and heat. The energy-exchange model includes slow phenomena described by the time-varying compliance plus a first approximation to quick release. To completely describe muscle's transient behavior, assumptions about crossbridge bonds were required. Identification of the mechanism behind these assumptions led to development of a large-scale distributed muscle model which focuses at the sarcomere level.

Physical description of the sarcomere adopts viscoelastic crossbridge bonds which form between interdigitating myofilaments. Myofilament mass and bond formation asynchrony, resulting from finite activation rate, lead to small myofilament motions in the form of damped vibrations. These vibrations lead to bond detachment and muscle relaxation.

Despite computational limitations, the distributed model describes both slow and quick phenomena with a single set of assumptions. It provides a single comprehensive description of muscle contraction and relaxation and predicts new features of the contractile mechanism. The latter includes a mechanism for muscle relaxation, prediction of muscle heat generation, a mechanism for stability of the thick filament within the sarcomere and prediction of muscle contraction sensitivity to ultrasound irradiation. The last effect was demonstrated for beating frog hearts.

Notes:

Thesis (Ph.D. in Bioengineering) -- Graduate School of Arts and Sciences, University of Pennsylvania, 1990.

Source: Dissertation Abstracts International, Volume: 51-08, Section: B, page: 3957.

Supervisor: Abraham Noordergraaf.

Local Notes:

School code: 0175.

Access Restriction:

Restricted for use by site license.