Development of a new conductance catheter system taking account of heterogeneous current distribution

1.利用简化的心室和胸腔形状模型，我们数值分析了电流在心室腔、心肌和周围组织中响应导管末端电刺激的非均匀分布。1)数值分析和非线性分析的发展：在第一年，我们将问题描述为一个偏导数方程的解，Vxx+Vyy+Vzz=0，边界条件在心内膜Vn=0，在两个刺激电极V=+/-V0。由于其轴对称性质，我们使用柱坐标系表示方程，并代入t=log(r)，得到exp(-2t)Vtt+Vzz=0。这些考虑使我们找到了一种方法，可以用对数等间距有效地离散r。通过数值分析，我们确定了心室容积与心室电导之间的非线性关系。2)任意旋转形状下的数值分析：我们开发了一个分析任意旋转形状下电流分布和非线性的软件。3)体外非线性检验：采用电极宽度为1mm、电极间距为1mm的导管进行非线性检验。我们确认90%的电流被限制在距离导管3.3mm的范围内。与以前的报告相比，范围更大；然而与我们的数值相似；analysis2。我们开发了一个电导体积测量系统，其中交流电流的产生以及RMS值的测定是用计算机进行数字的。这使得小型化和节能成为可能，从而通过植入装置在有意识的小动物（如老鼠）体内进行连续的体积测量。与产生的交流电同步的数据采样使得两个频率下的均方根计算只需要加法和减法。

1.Using a simplified shape model of ventricle and thorax, we analyzed numerically how currents distribute heterogeneously over ventricular cavity, myocardium, and surrounding tissue in response to electrical stimulation from catheter ends.1)Development of numerical analysis and analysis of nonlinearity : In the first year, we characterized the problem as a solution of a partial derivative equation, Vxx+Vyy+Vzz=0 with boundary conditions Vn=0 at endocardium and V=+/-V0 at both stimulating electrodes. We expressed the equation using cylindrical coordinate system, due to its axisymmetrical nature, and substituted t=log(r), resulting in exp(-2t)Vtt+Vzz=0. These considerations led us to a method to efficiently discretize r with its logarithm equi-spaced. With this numerical analysis we identified the nonlinear relation between ventricular volume and its conductance.2)Numerical analysis in arbitray rotational shapes : We have developed a software to analyze current distribution and nonlinearity in arbitrary rotational shapes.3)Examination of nonlinearity in vitro : We examined the nonlinearity with a catheter of electrode width of 1mm and interelectrode distance of 1mm. We confirmed that 90% of currents were confined within 3.3mm from the catheter. Compared to the preveious reports, the range was wider ; however was similar to our numerical; analysis2.We developed a conductance volumetric system, in which generation of AC currents as well as determination of RMS values is performed digitally with a computer. This enables miniaturization and power-saving, and thereby continuous volumetry by an implanted device in a conscious small animals such as in rats. Data sampling synchronous to generated AC made RMS calculation at two frequencies possible with only addition and subtraction.