Sun W, Min X
Medtronic, Inc., Minneapolis, MN 55432, USA.
IEEE Trans Biomed Eng. 1997 Dec;44(12):1237-42. doi: 10.1109/10.649995.
Electrogram sensed by an intracardiac electrode has long been characterized based on two approaches: 1) presume that the electrode is very small and does not disturb the potential prior to applying the electrode, and 2) take an average of the prior potential over the electrode surface. In fact, any intracardiac sensing electrode has a finite surface area where electrical charges are induced and disturb the external potential field, thus, the sensed potential is different from the potential prior to placing the electrode. In this paper, an integral equation model is proposed based on the current continuity equation in homogeneous myocardial medium. The new model can accurately characterize the electrogram sensed by an electrode with a non-negligible surface area and a load impedance. The new model can be solved numerically via the method of moments to obtain the potential induced on the electrode surface by an arbitrary dipole volume source. As an application of the proposed theory, several electrode configurations with different loads have been analyzed with an intent to show that a finite electrode surface will significantly reduce the electrogram peak amplitude and slope, and a load impedance lower than 20 k omega will also degrade the electrogram sensitivity.
1）假定电极非常小，在放置电极之前不会干扰电位；2）对电极表面的先前电位取平均值。实际上，任何心内传感电极都有一个有限的表面积，在该表面积上会感应出电荷并干扰外部电位场，因此，所感知的电位与放置电极之前的电位不同。本文基于均匀心肌介质中的电流连续性方程提出了一个积分方程模型。新模型能够准确地表征由具有不可忽略表面积和负载阻抗的电极所感知的电图。新模型可以通过矩量法进行数值求解，以获得由任意偶极体体积源在电极表面感应出的电位。作为所提出理论的一个应用，分析了几种具有不同负载的电极配置，旨在表明有限的电极表面会显著降低电图的峰值幅度和斜率，并且低于20 kΩ的负载阻抗也会降低电图的灵敏度。
