Allaart C P, Sipkema P, Westerhof N
Laboratory for Physiology, Free University, Amsterdam, The Netherlands.
Am J Physiol. 1995 Mar;268(3 Pt 2):H945-54. doi: 10.1152/ajpheart.1995.268.3.H945.
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.
通过间隔动脉用晶体溶液灌注大鼠心脏，对6个离体右心室乳头肌进行灌注，研究其对舒张期肌肉特性的影响。在不同灌注压力下获得应力-应变关系。灌注压力增加导致大应变时应力增加，但小应变时应力降低。因此，无应力应变随灌注压力增加而增加。在不同灌注压力（12-122 cmH₂O范围）下，给定肌肉的应力-应变关系在单一“交叉”应变处相交。定义为应力-应变关系斜率的肌肉僵硬度在所有应变下均增加。肌肉直径测量表明，观察到的应力-应变关系变化与血管充盈有关，而非与水肿形成有关。为了解释这些发现，将乳头肌建模为两个平行的隔室：肌肉细胞（连同细胞外基质）和脉管系统。假设灌注对轴向血管特性有影响，但对肌肉细胞无影响。肌肉隔室和血管隔室的应力-应变数据（取自文献）相结合，预测出的应力-应变关系与我们在灌注乳头肌中获得的关系相似。我们得出结论，灌注压力增加时肌肉僵硬度增加主要是由血管隔室力学行为的压力依赖性变化引起的。
