Coronary sinus pacing: Its influence on external and intraatrial signal-averaged P wave time domain parameters.

BACKGROUND The coronary sinus (CS) was, for 10 years, the standard place for permanent atrial pacing, and the antiarrhythmic properties of CS pacing were described by Moss in the early 70's. These observations were confirmed during EP studies, although currently permanent CS pacing is infrequently applied. Signal averaged (SA) P wave analysis has established values for the examination of EP properties of atrial myocardium. The aim of our study was to estimate the effect of CS pacing on the signal-averaged P wave recorded from external and intraatrial leads. METHODS Recordings were performed in 24 patients during biatrial pacing system implantation. A surface SA-ECG was obtained from orthogonal leads, and intraatrial signals were recorded and processed separately from the right and left atrium at SR and CS 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 Coronary sinus pacing favourably modifies SA P wave parameters of the left atrium; it significantly shortens Pdur, distinctly increases RMS20, decreases LAS5 and eliminates ALP in most patients in comparison to SR. It indicates beneficial effects of CS pacing on left atrial excitation and may explain its antiarrhythmic effect. Coronary sinus pacing does not deteriorate right atrium activation; it even slightly increases RMS20 and shortens the duration of LAS5 in RA in comparison to SR. Our findings suggest that CS is still an attractive site for permanent atrial pacing in patients with atrial arrhythmias and atrial conduction disturbances. (Cardiol J 2007; 14: 470-481).