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Intracellular Calcium and the Mechanism of the Dip in the Anodal Strength-Interval Curve in Cardiac Tissue

机译:心脏组织中细胞内钙和阳极强度-时间间隔曲线的下降机理

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Background: ?The strength-interval (SI) curve is an important measure of refractoriness in cardiac tissue. The anodal SI curve contains a “dip” in which the S2 threshold increases with interval. Two explanations exist for this dip: (1) electrotonic interaction between regions of depolarization and hyperpolarization; and (2) the sodium-calcium exchange (NCX) current. The goal of this study is to use mathematical modeling to determine which explanation is correct. Methods and Results: ?The bidomain model represents cardiac tissue and the Luo-Rudy model describes the active membrane. The SI curve is determined by applying a threshold stimulus at different time intervals after a previous action potential. During space-clamped and equal-anisotropy-ratios simulations, anodal excitation does not occur. During unequal-anisotropy-ratios simulations, electrotonic currents, not membrane currents, are present during the few milliseconds before excitation. The dip disappears with no NCX current, but is present with 50% or 75% reduction of it. The calcium-induced-calcium-release (CICR) current has little effect on the dip. Conclusions: ?These results indicate that neither the NCX nor the CICR current is responsible for the dip in the anodal SI curve. It is caused by the electrotonic interaction between regions of depolarization and hyperpolarization following the S2 stimulus.??( Circ J ?2014; 78: 1127–1135)
机译:背景:强度间隔(SI)曲线是衡量心脏组织难治性的重要指标。阳极SI曲线包含一个“ dip”,其中S2阈值随间隔增加。对于这种倾角存在两种解释:(1)去极化和超极化区域之间的电子相互作用; (2)钠钙交换(NCX)电流。这项研究的目的是使用数学模型来确定哪种解释是正确的。方法和结果:?双畴模型代表心脏组织,而Luo-Rudy模型描述活性膜。通过在先前动作电位之后的不同时间间隔应用阈值刺激来确定SI曲线。在空间限制和等各向异性比模拟中,不会发生阳极激发。在各向异性各向异性比的模拟过程中,在激发前的几毫秒内存在着电子电流,而不是膜电流。在没有NCX电流的情况下,该下降消失了,但是下降了50%或75%。钙诱导的钙释放(CICR)电流对下降的影响很小。结论:这些结果表明,NCX电流和CICR电流都不是阳极SI曲线下降的原因。它是由S2刺激后去极化和超极化区域之间的电声相互作用引起的。(Circ J?2014; 78:1127-1135)

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