Beyar R, Ben-Ari R, Gibbons-Kroeker C A, Tyberg J V, Sideman S
Julius Silver Institute, Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa.
Cardiovasc Res. 1993 Dec;27(12):2254-63. doi: 10.1093/cvr/27.12.2254.
The aim was to study the effects of the collagen mesh that interconnects the myocardial fibres on left ventricular mechanics and intramyocardial pressure.
An earlier model which integrates a symmetrical left ventricular geometry and transmural muscle fibre structure with muscle fibre mechanics was expanded to include radial stiffness generated by dynamically stretched radial collagen fibres. The calculated end systolic pressure-volume relationship (ESPVR) was compared to left ventricular pressure and volume data from six open chest dogs, obtained over a wide load range. Midwall intramyocardial pressure measurements by flat intramyocardial transducer in six different dogs were also used.
Consistent with the experiments, inclusion of radial stiffness yielded an ESPVR that was more curvilinear than the collagen-free model, and modified global left ventricular function in that the end systolic volume increased. A diastolic suction effect, manifested by a negative pressure with a steep diastolic pressure-volume relationship at low end systolic volumes, was predicted. The intramyocardial pressure was higher than the left ventricular pressure at the end of isovolumetric relaxation, when radial stretch is maximal and fibre stresses are relaxed. This is attributed to the radial fibre stress component. Intramyocardial pressure was only weakly dependent on left ventricular cavity pressure under wide load manipulations at constant contractility. The experiments also confirmed model predictions that (1) peak intramyocardial pressure is insensitive to load, (2) intramyocardial pressure is markedly higher than left ventricular pressure at the end of isovolumetric relaxation, and (3) intramyocardial pressure continues to rise during ejection towards a maximum value near end ejection.
The transverse radial stiffness due to radial collagen interconnections between myocardial fibrils affects the global systolic left ventricular function, the diastolic suction effect, and the mechanism of systolic coronary compression.
研究连接心肌纤维的胶原网对左心室力学和心肌内压力的影响。
一个早期模型整合了对称的左心室几何形状、透壁肌纤维结构和肌纤维力学，现进行扩展以纳入动态拉伸的径向胶原纤维产生的径向刚度。将计算得到的收缩末期压力-容积关系（ESPVR）与六只开胸犬在较宽负荷范围内获取的左心室压力和容积数据进行比较。还使用了六只不同犬的扁平心肌内换能器进行的心肌中层压力测量。
与实验结果一致，纳入径向刚度后产生的ESPVR比无胶原模型更呈曲线形，并改变了整体左心室功能，即收缩末期容积增加。预测了一种舒张期抽吸效应，在低收缩末期容积时表现为负压，舒张期压力-容积关系陡峭。在等容舒张末期，当径向拉伸最大且纤维应力松弛时，心肌内压力高于左心室压力。这归因于径向纤维应力分量。在恒定收缩性的广泛负荷操作下，心肌内压力仅微弱依赖于左心室腔压力。实验还证实了模型预测，即（1）心肌内压力峰值对负荷不敏感，（2）等容舒张末期心肌内压力明显高于左心室压力，（3）射血期间心肌内压力持续上升，在射血末期接近最大值。
心肌原纤维之间的径向胶原连接产生的横向径向刚度影响左心室整体收缩功能、舒张期抽吸效应和收缩期冠状动脉压缩机制。
