A new pacing mode which significantly reduced atrial pacing threshold, the 'overlapping biphasic impulse' (OLBI) stimulation using the floating atrial dipole of a single-pass lead has been reported. In this study the performance of OLBI stimulation was evaluated up to one year follow-up. In 10 patients (5 men, 5 female, age 63+/- 13 years) with complete AV block, single-lead VDD systems with an additional atrial OLBI stimulation capability were implanted. Temporary atrial OLBI pacing and diaphragmatic stimulation thresholds, P and R wave amplitudes, lead impedance and ventricular pacing thresholds were determined during implantation, before hospital discharge and at 1, 3, 6, and 12 month follow-up. The mean atrial OLBI pacing threshold decreased significantly at 1 year follow-up with respect to the implantation and the hospital discharge values (2.1 +/- 0.5 V vs 2.6 +/- 0.7 V and 2.8 +/- 0.8 V, p<0.05). While five patients did not experience any diaphragmatic stimulation at the maximum atrial pacing voltage (4.8V) of Dromos SL M7 pacemaker during one year follow-up, the other five patients had a mean diaphragmatic stimulation threshold of 3.1 +/- 0.8 V. In two patients the atrial pacing threshold was close to the diaphragmatic stimulation threshold, so safe programming was possible in 8 (80%) patients. In conclusion, the OLBI configuration provides AV-synchronous dual chamber pacing with a single-pass lead also in long-term.