NDLI: Strain Softening in Rat Left Ventricular Myocardium

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Emery, J. L. McCulloch, A. D. Omens, J. H.
Copyright Year	1997
Abstract	We investigated whether strain softening (or the Mullins effect) may explain the reduced left ventricular stiffness previously associated with the strain-history-dependent preconditioning phenomenon. Passive pressure–volume relations were measured in the isolated, arrested rat heart during LV balloon inflation and deflation cycles. With inflation to a new higher maximum pressure, the pressure–volume relation became less stiff, particularly in the low (diastolic) pressure range, without a significant change in unloaded ventricular volume. In five different loading protocols in which the maximum passive cycle pressure ranged from 10 to 120 mmHg, we measured increases at 10 mmHg in LV volume up to 350 percent of unloaded volume that depended significantly on the history (p < 0.05) and magnitude (p < 0.01) of maximum previous pressure. Although a quasi-linear viscoelastic model based on the pressure-relaxation response could produce a nonlinear pressure–volume relation with hysteresis, it was unable to show any significant change in ventricular stiffness with new maximum pressure. We incorporated a strain softening theory proposed by Johnson and Beatty (1992) into the model by modifying the elastic response with a volume-amplification factor that depended on the maximum previous pressure. This model more accurately reproduced the experimentally observed behavior. Thus, the preconditioning behavior of the myocardium is better explained by strain softening rather than viscoelasticity and may be due to damage to elastic components, rather than the effects of viscous tissue components.
Starting Page	6
Ending Page	12
Page Count	7
File Format	PDF
ISSN	01480731
e-ISSN	15288951
Journal	Journal of Biomechanical Engineering
Volume Number	119
Issue Number	1
DOI	10.1115/1.2796067
Language	English
Publisher	The American Society of Mechanical Engineers
Publisher Date	1997-02-01
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Biological tissues Cycles Inflationary universe Myocardium Pressure Relaxation (Physics) Stiffness Viscoelasticity
Content Type	Text
Resource Type	Article
Subject	Physiology (medical) Biomedical Engineering

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