SHORT TIME-SCALE LEFT-VENTRICULAR SYSTOLIC DYNAMICS - EVIDENCE FOR A COMMON MECHANISM IN BOTH LEFT-VENTRICULAR CHAMBER AND HEART-MUSCLE MECHANICS
SHORT TIME-SCALE LEFT-VENTRICULAR SYSTOLIC DYNAMICS - EVIDENCE FOR A COMMON MECHANISM IN BOTH LEFT-VENTRICULAR CHAMBER AND HEART-MUSCLE MECHANICS
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DOI：
10.1161/01.res.68.6.1532
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发表时间：
1991-06-01
影响因子：
20.1
通讯作者：
KIRKPATRICK, RD
中科院分区：
文献类型：
--
作者：
CAMPBELL, KB;SHROFF, SG;KIRKPATRICK, RD
基于短时间尺度、小幅度的左心室压力/容积/流出行为由起源于心肌纤维的动态过程主导的前提下，建立了一个原型模型来预测容积扰动对压力的响应。在模型中，腔室压力被认为是处于承压状态的发电机数量和它们的平均体积分布的乘积，正如A.F.赫胥黎的肌肉理论，其中力等于连接的十字桥的数量和它们的平均线性畸变。此外，与肌肉理论一样，假设压力发生器在两种状态之间循环，即承压状态和非承压状态。实验在离体雪貂心脏中进行，在两种指定的流速（流量钳，-7和-14 ml/sec）下去除可变体积减量（0.01-0.12 ml）。分析了压力对体积去除的响应。虽然原型模型解释了压力响应的大部分特征，但观察到细微但系统的差异。流动的存在与否和流动的大小影响模型参数的估计。然而，当模型拟合到流量大小相似但体积变化不同的流夹时，参数的估计并没有不同。因此，原型模型的不足归因于对流量相关效应的错误表述，而不是对体积相关效应的错误表述。基于这些差异，建立了一个改进的模型，在简单的两状态循环方案中添加了一条通往第三状态的途径。这条路径仅在响应体积变化时才被遵循。改进后的模型消除了原型模型的不足，充分考虑了所有观测值。由于改进模型的模板取自肌肉收缩的循环交叉桥理论，因此可以得出结论，尽管左室的几何、结构和功能和结构的区域异质性具有复杂性，但交叉桥机制主导了左室行为的短时间尺度动力学。
Based on the premise that short-time-scale, small-amplitude pressure/volume/outflow behavior of the left ventricular chamber was dominated by dynamic processes originating in cardiac myofilaments, a prototype model was built to predict pressure responses to volume pertubations. In the model, chamber pressure was taken to be the product of the number of generators in a pressure-bearing state and their average volumetric distrotion, as in the muscle theory of A.F. Huxley, in which force was equal to the number of attached crossbridges and their average lineal distortion. Further, as in the muscle theory, pressure generators were assumed to cycle between two states, the pressure-bearing state and the non-pressure-bearing state. Experiments were performed in the isolated ferret heart, where variable volume decrements (0.01-0.12 ml) were removed at two commanded flow rates (flow clamps, -7 and -14 ml/sec). Pressure responses to volume removals were analyzed. Although the prototype model accounted for most features of the pressure responses, subtle but systematic discrepancies were observed. The presence or absence of flow and the magnitude of flow affected estimates of model parameters. However, estimates of parameters did not differ when the model was fitted to flow clamps with similar magnitudes of flows but different volume changes. Thus, prototype model inadequacies were attributed to misrepresentation of flow-related effects but not of volume-related effects. Based on these discrepancies, an improved model was built that added to the simple two-state cycling scheme, a pathway to a third state. This path was followed only in response to volume change. The improved model eliminated the deficiencies of the prototype model and was adequate in accounting for all observations. Since the template for the improved model was taken from the cycling crossbridge theory of muscle contraction, it was concluded that, in spite of the complexities of geometry, architecture, and regional heterogeneity of function and structure, crossbridge mechanisms dominated the short-time-scale dynamics of left ventricular chamber behavior.