Noninvasive recording of electrical activity in the PR segment in man.

Open Access
Publisher Website
Google Scholar
Abstract
A method is described for the noninvasive recording of electrical activity in the PR segment in man. Signals from chest surface electrodes, positioned on the basis of mapping experiments in 2 patients, were amplified 0.5-2.0 .times. 106 times and filtered to select frequencies from 40 to 500 Hz. Noise in the resulting signal was reduced using computerized digital averaging of 150 to 500 cycles. A time reference point, required for the averaging process, was derived from a change in slope of the QRS complex of a separate surface ECG. Digital filtering was used to eliminate high frequency residual noise after averaging. The system was shown to recover the surface deflection resulting from a His pacing stimulus of only 20 mV. Highly reproducible electrical deflections were recorded in the PR segment in 2 healthy male subjects on whom the method was initially developed. Of 11 similar subjects, 9 subsequently showed recognizable patterns of activity within the PR segment. External recordings were made in 10 patients undergoing simultaneous conventional His bundle electrography for conducting system disease. In 8, surface deflections were obtained synchronous with the internal His waveform. In 6 cases, the configuration of internal and external signals was very similar. In 5 patients additional activity of interest was recorded late in the PR segment.