High fidelity electrocardiography: Further studies including the comparative performance of four different electrocardiographs

The purpose of this paper is to compare the high fidelity response of four electrocardiographs which have four different types of galvanometers and to discuss certain other aspects of this subject. In a previous paper we reviewed the pertinent literature1–3 and reported the results of our studies4 of the standard extremity and precordial leads recorded by the cathode ray oscillograph (here-after referred to as C.R.O.) and a high speed camera. Records thus obtained are considerably expanded, being approximately six times the amplitude and twelve times the width of conventional records. In such records high frequency components of at least 500 cycles per second and probably more are revealed. This instrument is the criterion for high fidelity response with which the other three electrocardiographs will be compared.