Abstract. Interatrial conduction disturbances are known substrate of re-entrant atrial arrhythmias and their diagnosis is important for the optimal therapy choice. Signal averaged (SA) P wave analysis is proved to be very useful for selection of patients with high risk of atrial arrhythmias. It allows recognizing important substrate for atrial arrhythmias – local conduction disturbances with micro-voltage oscillations during final part of atrial excitation. Biatrial pacing created the new therapeutic chance for pts with atrial arrhythmias but until now there were no studies to evaluate its effects by means of P wave SA ECG and SA IEGM analysis.

The aim of our study was to estimate the effect of BiAP on SA P wave recorded from external and from intraatrial leads.

Methods. We examined 24 pts with IACD during biatrial pacing system implantation. Intraatrial signals were recorded separately from right and left atrium, using bipolar pacing leads placed in RAA and CS and ventricular lead temporary placed in LRA site. External signals were obtained from Frank leads. Signals were obtained during sinus rhythm (SR) and BiAP. Signals were filtered and recorded with Codax SAI-IK amplifier, digitized by A/D converter and stored on PC. We analyzed following SAECG parameters: P wave duration (Pdur), root mean square voltages of the last 20 ms of P wave (RMS20) and duration of low amplitude signal <5uV (LAS5). We considered ALP as positive if Pdur >125ms and RMS20 <2,40uV.

Results.

Conclusions. 1. BiAP favorable modifies SA time domain parameters of right and left atrium. 2. BiAP significantly shortens P duration, increases significantly RMS20, eliminates atrial late potentials in most patients and distinctly decreases duration of LAS5 in comparison to SR. 3. It occurs in both right and left atrium, confirming beneficial effect of BiAP on atrial excitation, which can explain its antiarrhythmic effect. 4. In spite of effective simultaneous pacing of both atria, in about 50% of pts symptoms of local conduction disturbances with micro-voltage oscillations during final part of atrial excitation remain still present, which can be observed mainly in intraatrial recordings from RA leads. Significance of this phenomenon needs further observations.