Beat to beat surface recording and averaging of His-Purkinje activity in man

A non-invasive technique has been used to record the electrical activity of the His-Purkinje System (HPS) on the body surface involving shielding, high gain band pass filtering and averaging of bipolar chest ECGs (V6-V6R). The measurements were made in the Berlin Magnetically Shielded Room (BMSR) which reduces the background noise level (almost white) to less than 0.4 microVrms (measured for a bandwidth between 0.1 Hz and 300 Hz), so that individual HPS body surface signals were limited only by patient inherent noise. Signal amplitudes greater than 1 microV were detectable in single beats. In addition, for best resolution, signal averaging was accomplished with software triggers referred to either the QRS complex or the P wave. A P-wave trigger is of most interest in clinical use because averaging techniques, even in the case of A-V blocks of different degree, can be applied.