Derivation and left ventricular pressure phase plane based validation of a time dependent isometric crossbridge attachment model.
Derivation and left ventricular pressure phase plane based validation of a time dependent isometric crossbridge attachment model.
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基于时间相关等距横桥连接模型的推导和左心室压力相平面验证。
DOI：
10.1007/s10558-006-9020-6
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发表时间：
2006
影响因子：
--
通讯作者：
Kovacs,SandorJ
中科院分区：
文献类型：
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作者：
Zhang,Wei;Chung,CharlesS;Kovacs,SandorJ
赫胥黎的横桥附着模型预测张力（收缩力）的发展等长（固定长度）细胞使用恒定的附着和脱离率。包含随时间变化的钙浓度的替代模型是复杂的（耦合线性微分方程），并且使用时间依赖性输入（钙、弹性等）。来模拟多个状态。我们假设，通过将已知的细胞内钙的显著上升和下降，经由不对称阻尼函数或对称高斯函数，纳入随时间变化而不是恒定的附着率函数，Huxley模型对张力的预测（即，等容（等长）非射血搏动中的室压）将得到改善。为了检验时间依赖性模型预测（TDM）压力比恒定附着率预测压力更适合体内等容（等容）LV压力相平面（PPP）轮廓的假设，我们使用TDM来拟合6例受试者的非射血性室性早搏（PVC）PPP轮廓。传统模型拟合较差（相对误差74.0%±12.5%），而非对称阻尼TDM速率函数相对于传统的时间无关模型（相对误差55.4%±9.8%）略有改善。对称高斯频率函数TDM为所有测试的非喷射性搏动提供了最佳PPP拟合（相对误差19.8%±4.8%）。我们的结论是，通过一个随时间变化的，而不是恒定的，速率函数近似的集总附着率产生一个生理上可行的模型的过桥行为。PPP提供了最佳的竞技场，用于通过时间依赖性附着率函数进行LVP轮廓预测的替代数学公式评估，并有助于心脏收缩和舒张的建模。
Huxley’s crossbridge attachment model predicts tension (contractile force) development in isometric (fixed length) cells using constant attachment and detachment rates. Alternative models incorporating time-varying calcium concentrations are complex (coupled linear differential equations) and use time-dependent inputs (calcium, elastance, etc.) to model multiple states. We hypothesize that by incorporating the known significant rise and fall in intracellular calcium, via either an asymmetric damped function or a symmetric Gaussian function, into a time-varying, rather than constant, attachment rate function, the Huxley model prediction for tension (i.e., chamber pressure) in isovolumic (isometric) non-ejecting beats will improve. To test the hypothesis that the time-dependent model-predicted (TDM) pressure fits the in vivo isometric (isovolumic) LV pressure phase-plane (PPP) contour better than the constant attachment rate predicted pressure, we used the TDM to fit non-ejecting, premature ventricular contraction (PVC) PPP contours in 6 subjects. Conventional model fit was poor (relative error 74.0%±12.5%), while the asymmetric damped TDM rate function provided slight improvement relative to the conventional time-independent model (relative error 55.4%±9.8%). The symmetric Gaussian rate function TDM provided the best PPP fit to all non-ejecting beats tested (relative error 19.8%±4.8%). We conclude that approximating the lumped attachment rate via a time-varying, rather than constant, rate function generates a physiologically viable model of crossbridge behavior. The PPP provides the optimal arena for alternate mathematical formulation assessment of LVP contour prediction by time-dependent attachment rate functions and facilitates modeling of cardiac contraction and relaxation.