Measurement And Calculation Of The
Intramyocardial Stress
Author(s)
S. Mihailescu & R. M. Shoucri
Abstract
By using a servo-nulling mechanism and coated glass micropipettes (20-24 µm
OD), intramyocardial stress (IMS) was measured at the base of the left ventricle
in isolated working and nonworking cat hearts, perfused with Krebs-Henseleit
buffer. Glass micropipettes were placed at various depths inside the left
ventricular wall using a micropipette holder and manipulator. Calculation of the
IMS is not a simple problem because of the complex structure of the active fibres
in the myocardium. However a mathematical approach has been developed that
reduces the complexity of this problem. It consists in using the concept of force
per unit volume of the myocardium to model the components of the stress
generated by the fibers in three orthogonal directions (assuming symmetrical
contraction). Important relations are derived between the stress induced by the
LVP and the stress induced by the active fibres in the passive medium of the
myocardium.
Keywords: measurement with micropipette, intramyocardial stress, active and
passive stress in the myocardium, left ventricular elastance, active force per unit
volume of the myocardium, stress-strain relation in the myocardium.
1 Introduction
Contraction of myocardial fibers creates the hydraulic pressure necessary for
displacement of blood inside the cardiovascular system. A side effect of left
ventricular contraction is the compression of its coronary vessels, which results
in a fasic reduction of its coronary arterial flow [1]. Systolic closure of left
Keywords
measurement with micropipette, intramyocardial stress, active and
passive stress in the myocardium, left ventricular elastance, active force per unit
volume of the myocardium, stress-strain relation in the myocardium.
Related Book
Other papers in this volume
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