Background: Conventional right atrial appendage pacing (RAAp) eliminates the electrophysiological consequences of bradycardia only, leading to suppression of the rhythm-dependent arrhythmias but in some patients RAAp may increase AF recurrences or even promote it in patients without AF history. Relatively rare incidence of AF in patients implanted with single lead VDD pacing system may indicate RAAp influence. Atrial conduction disturbances (ACD) are the known substrate of re-entrant atrial arrhythmias and their detection is important for the selection of proper therapy. Time-domain analysis of P-wave in signal-averaged ECG (SA-ECG) recorded from chest leads is an accepted method evaluating inhomogeneity of atrial excitation, predictive for atrial arrhythmias. The aim of our study was to estimate the effect of RAAp on SA-ECG recorded from conventional external and from 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 averaged separately from the right and left atrium at SR and RAAp (LA pacing was temporary switched). 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 µV).
Results and conclusions: RAAp significantly prolongs all parameters reflecting atrial activation (P ECG, TAAT, SA-ECG Pdur, SA-IEGM Adur in RA and LA) by 20 to 30 ms in comparison to SR. RAAp decreases RMS20 and prolongs LAS5 values both in external and intraatrial leads, which reflects increased micro-oscillations in the final portion of atrial potential. The lower RMS20 and higher LAS5 values in RA compared to LA suggest less homogenous depolarization in right atrium. This may suggest that atrial activation extinguishes more homogenously in LA. A different explanation may be that the observed sluggish ending of RA signal may be the result of a far-field sensing from the LA. The strong correlations between RAA paced P wave, TAAT, SA-ECG Pdur, SA-IEGM RA and LA Adur confirm that those parameters reproduce mostly the velocity of conduction within the atria. Our findings indicates significant aggravation of ACD (mainly in RAA) and suggests that the search is needed for another RA lead location for permanent single site and biatrial pacing. (Cardiol J 2007; 14: 372-383)