Abstract. Conventional time-domain analysis of signal-averaged (SA) ECG recorded from Frank’s chest leads is accepted method of evaluation of inhomogeneity of atrial excitation, predictive for atrial arrhythmias. Its main disadvantages are poor atrial signal, QRS complex discrimination and necessity of synchronization using R wave. We put the hypothesis that analysis of high gain SA of right- and left atrial potentials leads to better recognition of local conduction disturbances with micro-voltage oscillations during final part of atrial excitation (evaluated by root mean square voltages of the last 20 ms of A wave - RMS 20 and duration of low amplitude signal < 5uV - LAS 5).

The aim of the study was to determine value of SA intra-atrial signals for technique for recognition of atrial late potentials and its comparison to conventional technique.

Methods. Intra-atrial signals were recorded in 24 pts with interatrial conduction disturbances during implantation of BiA pacemaker, using bipolar leads (designed for permanent pacing) located in RAA, LRA and CS. Before implantation standard surface SA ECG from orthogonal Frank leads was obtained. We analyzed following parameters: P wave duration (Pdur), RMS20 and LAS5 and presence of ALP criteria in records obtained from external as well as right- and left intra-atrial leads.

Conclusion. Intra-atrial SA IEGM yields accurate data for ALP study, mostly due to better signal quality and QRS discrimination. P duration and RMS20 seem to be substantial parameters with good correlation between external SA ECG and internal SA IEGM, however the last method requires establishing definite evaluation criteria.