Change in surface and intraatrial signal-averaged P-wave during biatrial pacing

High gain, signal-averaged ECG using standard surface lead technique (using 3 orthogonal chest Frank's leads) and intraatrial (using 3 orthogonal intraatrial leads: RAA, LRA, CS connected adequately) were recorded in 24 pts during implantation of biatrial pacing system. P (A wave) amplitude was remarkably higher using intraatrial technique than using conventional one; the amplitude of QRS (V wave) was lower, P/QRS (A/V) ratio was much more favourable and noise level was lower using intraatrial lead technique. Moreover, intraatrial A wave provides excellent trigger for the averaging process. Described procedure of recording of high gain, signal-averaged ECG seems to be very useful for exact evaluation of terminal portion of atrial. activation and may be a valuable diagnostic and scientific tool.