AJP - Heart and Circulatory Physiology, Vol 249, Issue 2 222-H230, Copyright © 1985 by American Physiological Society
Biaxial mechanical properties of the pericardium in normal and volume overload dogs
M. C. Lee, M. M. LeWinter, G. Freeman, R. Shabetai and Y. C. Fung
The two-dimensional mechanical properties of the pericardium from dogs with
a normal or chronically enlarged heart were studied in vitro. A
3.0-cm-square piece of the pericardium overlying the right and/or left
ventricle was excised. An approximately 1.0-cm-square target was marked at
the center, and its dimension was measured electrooptically. When immersed
in physiological saline at 37 degrees C, the specimen was stretched and
unloaded sinusoidally in one direction while force in the transverse
direction was held constant. The tension-stretch relationship was highly
reproducible and was insensitive to strain rate in the range of 0.002-0.1
Hz. Hysteresis was present. The pericardium was mostly anisotropic;
however, the direction of maximal compliance varied among dogs. The elastic
properties of the pericardium overlying the left and right ventricles were
the same in most cases. Substantial stress relaxation was observed; in
contrast, insignificant creep developed over 30 min. In five dogs with
chronic cardiac dilatation due to an infrarenal aortocaval shunt, the
tension-stretch curves were shifted significantly to the right (i.e.,
greater deformation at the same tension level). However, the pericardial
viscoelastic properties and thickness were unchanged. In other words,
chronic cardiac dilatation resulted in a more compliant pericardium.
