Study of High Frequency Components in Electrocardiogram by Power Spectrum Analysis

• In a paper read before the Chelsea Clinical Society on March 19, 1912, Binthoven stated that a string galvanometer, with a deflecting time of 0.01 sec./mm. when standardized in the usual manner, was adequate to record the form and dimensions of the electrocardiogram.* He further stated that if the string could be made 10 or 100 times faster, the sensitivity remaining constant, no perceptible change would be noted in the record. This conclusion remained unchallenged until 1933, when Reid and Caldwell reopened the issue. Using a vacuum tube amplifier and a bifilar oscillograph, they showed in a tracing taken on a normal subject that the one hundredth harmonic was twice as large as the fundamental. Since then, although a number of workers have examined the problem," the issue remains open. It is not, however, the purpose of this investigation to shed new light on the proper techniques for recording the form and dimensions of the conventional electrocardiogram, but rather by a new method to explore the possibility that the higher frequency components may contain useful information. This approach was suggested to us particularly by the work of Langner, in which he showed beading and notching of the QTCS complex in patients with ischemic heart disease."