Tayler D I, Vincent R
Br Heart J. 1985 Aug;54(2):121-8. doi: 10.1136/hrt.54.2.121.
Specifications recommended for electrocardiographs omit any reference to phase characteristics and place undue emphasis on an extended amplitude response. This does not, however, ensure faithful reproduction of the electrocardiogram and may result in less effective attenuation of unwanted noise than can be achieved with modern filters. The separate effects of phase and amplitude response on electrocardiographic signals were compared, and it was shown that distortion of the electrocardiogram by equipment with an inadequate phase response may cause changes resembling those seen in ischaemic heart disease. Case reports are presented in which distortion produced by commercial equipment impeded diagnosis. Specifications recommended as standard for electrocardiographs should be modified to include phase response and allow greater attenuation of frequencies below 0.5 Hz.
心电图机推荐规范未提及任何相位特性，而是过度强调扩展的幅度响应。然而，这并不能确保心电图的忠实再现，并且与现代滤波器相比，可能导致对不需要噪声的衰减效果较差。比较了相位和幅度响应对心电图信号的单独影响，结果表明，相位响应不足的设备对心电图的失真可能会导致类似于缺血性心脏病所见的变化。本文给出了一些病例报告，其中商用设备产生的失真妨碍了诊断。推荐作为心电图机标准的规范应进行修改，以纳入相位响应，并允许对低于0.5Hz的频率进行更大程度的衰减。
