Campbell K B, Taheri H, Kirkpatrick R D, Burton T, Hunter W C
Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman 99164-0001.
Am J Physiol. 1993 Jun;264(6 Pt 2):H1926-41. doi: 10.1152/ajpheart.1993.264.6.H1926.
The frequency-dependent dynamic elastance of the left ventricle (LV) of isolated rabbit heart was determined and compared with dynamic stiffness of excised rabbit papillary muscle. Comparison was made in three states: 1) relaxed, 2) BaCl2 contracture, and 3) rigor. Dynamic chamber elastance was determined by pressure-to-volume ratio at 12 frequencies of sinusoidal volume variation between 0.1 and 30 Hz. Dynamic elastance during BaCl2 contracture was distinctly different from that during either relaxed or rigor states. Characteristics of BaCl2 contracture were 1) as frequency increased, polar plot of real and imaginary elastance showed a progressively opening clockwise spiral that tended eventually to become tangent to the apogee of a semi-circle by 30 Hz; 2) modulus spectrum exhibited asymptotes at low and high frequencies with an intervening dip to a minimum at 1.25 Hz; and 3) phase showed a sharp transition at dip frequency from small negative values at lower frequencies to large positive values at intermediate frequencies and then declined at highest frequencies. There was little dependence of dynamic elastance on frequency in both relaxed and rigor states. Dynamic muscle stiffness exhibited all features of dynamic chamber elastance in all three states. We concluded that dynamic elements responsible for myofiber stiffness were also responsible for LV chamber elastance. Furthermore, it was possible to describe and interpret dynamic chamber elastance and muscle stiffness with a common model based on muscle cross-bridge theory. This model did a reasonable job of reproducing all important features of experimentally observed LV chamber elastance and muscle stiffness. Thus dynamic homologies between chamber and muscle were established in experimental data and in the fact that a single interpretive model served equally well for both chamber elastance and muscle stiffness.
测定了离体兔心脏左心室（LV）的频率依赖性动态弹性，并与离体兔乳头肌的动态刚度进行了比较。在三种状态下进行了比较：1）松弛状态，2）BaCl₂ 挛缩状态，3）强直状态。通过在0.1至30Hz之间的12个正弦体积变化频率下的压力-体积比来测定动态心室弹性。BaCl₂ 挛缩状态下的动态弹性与松弛状态或强直状态下的动态弹性明显不同。BaCl₂ 挛缩的特征为：1）随着频率增加，实部和虚部弹性的极坐标图显示出逐渐顺时针打开的螺旋，到30Hz时最终趋于与半圆的顶点相切；2）模量谱在低频和高频处呈现渐近线，在1.25Hz处有一个中间凹陷至最小值；3）相位在凹陷频率处有一个急剧转变，从较低频率的小负值变为中间频率的大正值，然后在最高频率处下降。在松弛状态和强直状态下，动态弹性对频率的依赖性很小。在所有三种状态下，动态肌肉刚度都表现出动态心室弹性的所有特征。我们得出结论，负责肌纤维刚度的动态元件也负责左心室腔弹性。此外，基于肌肉横桥理论，有可能用一个通用模型来描述和解释动态心室弹性和肌肉刚度。该模型在重现实验观察到的左心室腔弹性和肌肉刚度的所有重要特征方面表现良好。因此，在实验数据中以及在一个单一的解释模型对心室弹性和肌肉刚度同样适用这一事实中，建立了心室和肌肉之间的动态同源性。
