Effect of perfusion pressure on diastolic stress-strain relations of isolated rat papillary muscle.
The effect of perfusion on diastolic muscle properties was investigated in six isolated right ventricular papillary muscles from rat hearts perfused with a crystalloid solution via the septal artery. Stress-strain relations were obtained at different perfusion pressures. Increased perfusion pressure caused an increase of stress at large strains but a decrease of stress at low strains. Thus stress-free strain increased with increasing perfusion pressure. Stress-strain relations of a given muscle at different perfusion pressures (range 12-122 cmH2O) intersected at a single "crossover" strain. Muscle stiffness, defined as the slope of the stress-strain relation, increased at all strains. Muscle diameter measurements indicated that the observed changes of the stress-strain relation occurred in association with vascular filling rather than with formation of edema. To explain the findings, the papillary muscle was modeled by two parallel compartments: muscle cells (together with the extracellular matrix) and vasculature. Perfusion was assumed to have an effect on the axial vascular properties but not on muscle cells. Combination of the stress-strain data of the muscle compartment and the vascular compartment (taken from literature) predicted stress-strain relations similar to those obtained in our perfused papillary muscles. We conclude that increased muscle stiffness at increased perfusion pressure is mainly caused by pressure-dependent changes in mechanical behavior of the vascular compartment.
Allaart
C P
CP
Laboratory for Physiology, Free University, Amsterdam, The Netherlands.
Sipkema
P
P
Westerhof
N
N
D000818:Animals; D003971:Diastole / Q000502:physiology; D004487:Edema / Q000503:physiopathology; D004548:Elasticity; D066298:In Vitro Techniques; D008297:Male; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology; D010210:Papillary Muscles / Q000502:physiology*; D010477:Perfusion / Q000295:instrumentation; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D014783:Viscosity