Effects of different atrial pacing modes evaluated by intracardiac signal-averaged ECG.

BACKGROUND Analysis of high gain, signal-averaged (SA) ECG is an accepted method evaluating abnormalities of atrial repolarization--the presence of late potentials (ALP)--predictive for atrial arrhythmias. Recently it has been proven that the location of atrial leads has an influence on atrial activation and modifies the risk of atrial arrhythmias. The aim of our study was to estimate the effect of different modes of atrial pacing on signal-averaged P waves recorded from external (conventional) and from intra-atrial leads. METHODS Recordings were performed in 24 patients during biatrial (BiA) pacing system implantation. A surface SA-ECG was obtained from orthogonal leads, and intra-atrial signals were recorded and averaged separately from the right and left atrium during sinus rhythm (SR) and atrial pacing from the right atrial appendage, coronary sinus or both (BiA pacing). We analyzed standard SA-ECG parameters (P/A wave duration, RMS20 and LAS5) and the presence of atrial late potentials (ALP-Pdur > 125 ms and RMS20 < 2.40 mV). RESULTS AND CONCLUSIONS Right atrial appendage pacing prolongs the duration of atrial potential in external and intracardiac leads and decreases its homogeneity in comparison to SR. RAA pacing increases the occurrence of ALP both in external and internal SA-ECG. Coronary sinus pacing does not deteriorate atrial activation in comparison to SR. Biatrial pacing shortens atrial potential, increases its homogeneity and eliminates atrial late potential criteria in most of patients in comparison to SR. It can be observed both in external and intra-atrial leads and confirms the beneficial effects of BiA pacing on atrial excitation, explaining its antiarrhythmic effect. Evaluation of signal-averaged intra-atrial electrograms supplies more data about local conduction disturbances with micro-voltage oscillations during final part of atrial excitation (low RMS20 and prolonged LAS5) than conventional techniques and seems to be a valuable tool for the evaluation of new resynchronizing atrial pacing modes.