Extracellular field required for excitation in three-dimensional anisotropic canine myocardium.
Extracellular field required for excitation in three-dimensional anisotropic canine myocardium.
复制标题
三维各向异性犬心肌激发所需的细胞外场。
DOI：
10.1161/01.res.63.1.147
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发表时间：
1988
影响因子：
20.1
通讯作者：
Ideker,RE
中科院分区：
文献类型：
--
作者：
Frazier,DW;Krassowska,W;Chen,PS;Wolf,PD;Dixon,EG;Smith,WM;Ideker,RE
目前尚不清楚电位梯度、电流密度和能量与原位心脏中细胞外刺激的兴奋之间的相关性。此外，尚未评估纤维取向和刺激极性对以这些因素表示的刺激的细胞外阈值的影响。为了回答这些问题，心肌电刺激，细胞外兴奋阈值测定的刺激电位和激活模式记录从120个透壁电极在一个35 × 20 × 5毫米的区域的右心室流出道在6个开胸犬。细胞外电位梯度，电流密度，能量，和它们的组件的纵向和横向的局部纤维的方向在每个记录站点计算3毫秒恒定电流刺激产生的刺激电位。将由刺激场直接激发的区域中的所得值与不直接激发但由远离直接激发区域的波前传播激活的区域中的值进行比较。电流密度为3.66 mA/cm 2，能量为9.7 microJ/cm 3，电位梯度为804 mV/cm，直接和非直接激发位点的最小错误分类分别为8%，13%和17%。电位梯度的纵向（l）和横向（t）分量的线性双变量组合产生7%的错误分类（阈值比t/l为2.88），相应电流密度分量的线性组合产生8%的错误分类（阈值比t/l为1.04）。阳极和阴极阈值无显著差异（p = 0.39）。针对0.2-20毫秒的脉冲持续时间（D）构建电位梯度、电流密度和能量强度-持续时间曲线。电流密度大小（Jm）的最佳拟合双曲线为Jm = 3.97/D + 3.15，其中Jm以mA/cm 2为单位，D以msec为单位。因此，对于电刺激期间的刺激，1）电流密度大小以及电位梯度的纵向和横向分量都与激发密切相关，2）沿着心脏细胞的细胞外电位梯度具有比跨细胞低的阈值，而沿着和跨细胞的电流密度阈值是相似的，3）对于大于或等于5 mA的刺激，阳极和阴极阈值近似相等，以及4）细胞外电位梯度、电流密度和能量激发阈值可以由强度-持续时间方程表示。
It is not known how well potential gradient, current density, and energy correlate with excitation by extracellular stimulation in the in situ heart. Additionally, the influence of fiber orientation and stimulus polarity on the extracellular thresholds for stimulation expressed in terms of these factors has not been assessed. To answer these questions for myocardium in electrical diastole, extracellular excitation thresholds were determined from measurements of stimulus potentials and activation patterns recorded from 120 transmural electrodes in a 35 X 20 X 5-mm region of the right ventricular outflow tract in six open-chest dogs. Extracellular potential gradients, current densities, energies, and their components longitudinal and transverse to the local fiber orientation at each recording site were calculated from the stimulus potentials produced by 3-msec constant-current stimuli. The resulting values in regions directly excited by the stimulus field were compared with the values in regions not directly excited but activated by the spread of wavefronts conducting away from the directly excited region. Magnitudes of 3.66 mA/cm2 for current density, 9.7 microJ/cm3 for energy, and 804 mV/cm for potential gradient yielded minimum misclassifications of 8%, 13%, and 17%, respectively, of sites directly and not directly excited. A linear bivariate combination of the longitudinal (l) and transverse (t) components of the potential gradient yielded 7% misclassification (threshold ratio t/l of 2.88), and linear combination of corresponding current density components yielded 8% misclassification (threshold ratio t/l of 1.04). Anodal and cathodal thresholds were not significantly different (p = 0.39). Potential gradient, current density, and energy strength-duration curves were constructed for pulse durations (D) of 0.2-20 msec. The best fit hyperbolic curve for current density magnitude (Jm) was Jm = 3.97/D + 3.15, where Jm is in mA/cm2, and D is in msec. Thus, for stimulation during electrical diastole 1) both current density magnitude and longitudinal and transverse components of the potential gradient are closely correlated with excitation, 2) the extracellular potential gradient along cardiac cells has a lower threshold than across cells, while current density thresholds along and across cells are similar, 3) anodal and cathodal thresholds are approximately equal for stimuli greater than or equal to 5 mA, and 4) the extracellular potential gradient, current density, and energy excitation thresholds can be expressed by strength-duration equations.