Lu R M, Steinhaus B M
Research and Development, Telectronics Pacing Systems, Englewood, CO 80112.
Biomed Instrum Technol. 1993 Jan-Feb;27(1):64-8.
This study investigated computer simulations and animal studies of a simple digital notch filter to remove 50-and 60-Hz line-frequency-noise interference. The digital notch filter was achieved by computing running subtraction of the intracardiac electrogram and the electrogram recorded one notch-sample period previously. Simultaneous rejection of the two worldwide line frequencies was obtained by computation of the minimum of two separate notch-filter outputs. Power consumption of this numerical algorithm was reduced for applications in implantable devices by operating the notch filters only from 20 msec to 50 msec after a sense event. A sense event was classified as a noise sense if the sum of notch-filter output during this window was less than a preset threshold of the sum of the raw data during the same time window. Otherwise, the sense event was classified as a true sense. The computer simulations determined an optimum threshold value of 33%. The filter was tested in five animal studies using a signal generator to inject additive noise interference. The results indicated that this simple filter could be implemented in an implantable pulse generator and could effectively exclude incorrect line-frequency-noise senses at the notched frequencies.
本研究调查了一种简单数字陷波滤波器的计算机模拟和动物实验，以去除50赫兹和60赫兹的电源频率噪声干扰。该数字陷波滤波器通过计算心内电图与前一个陷波采样周期记录的电图的连续减法来实现。通过计算两个单独陷波滤波器输出的最小值，同时抑制了全球范围内的两个电源频率。通过仅在感知事件发生后20毫秒至50毫秒操作陷波滤波器，降低了该数值算法在植入式设备中的功耗。如果该窗口内陷波滤波器输出的总和小于同一时间窗口内原始数据总和的预设阈值，则将感知事件分类为噪声感知。否则，将感知事件分类为真实感知。计算机模拟确定了33%的最佳阈值。使用信号发生器注入附加噪声干扰，在五项动物实验中对该滤波器进行了测试。结果表明，这种简单的滤波器可以在植入式脉冲发生器中实现，并能有效排除陷波频率处不正确的电源频率噪声感知。
