Electrical characteristics of low atrial septum pacing compared with right atrial appendage pacing.

AIM: The study was designed to compare the electrical characteristics of atrial leads placed in the low atrial septum (LAS) with those placed in the right atrial appendage (RAA) associated with dual chamber pacing. METHODS: In 86 patients an active-fixation (St. Jude Medical's Tendril DX model 1388T) atrial lead was positioned in RAA and in 86 patients the same model atrial lead was placed in the LAS. Pacing thresholds, sensing thresholds, impedances and the Far Field paced R-Wave (FFRW) amplitude and timing were compared at 6 weeks and at 3 and 6 months. RESULTS: The pacing threshold did not differ between groups. Sensed voltage of the P-wave was higher in the LAS compared with the RAA at 3 and 6 months (P=0.004). Impedance was higher in the LAS at 6 weeks and 3 months (P=0.002) but this difference was no longer significant at 6 months (P=0.05). The atrial sensed FFRW voltage was significantly higher in the LAS position compared with the RAA at 3 and 6 months follow-up (P=0.0002). FFRW voltage>1 mV was seen in 87% of the RAA pacing group and in 94% of the LAS pacing group (P=ns). The time between the ventricular pacing stimulus and the sensed FFRW in the atrium, (V spike-FFRW) in RAA was longer than in LAS at all follow-up measurements (P=0.006). CONCLUSIONS: The electrical characteristics of LAS pacing makes this alternative position in the atrium safe and feasible. Though statistical differences were found in P-wave sensing (LAS higher voltage than in the RAA) and FFRW sensing was higher in the LAS compared with the RAA this did not interfere with the clinical applicability of the LAS as alternative pacing site.