Far-field R-wave (FFRW) sensing of the atrial lead of AAI or DDD pacemakers causes incorrect mode switches and remains a problem in patients with atrial arrhythmias in whom low voltage sensing is essential. We studied a pacing electrode with a short tip-ring distance (1.1 mm). We compared our findings with recordings from a conventional electrode with a larger tip-ring distance (10 mm).Methods
Thirty-six consecutive patients with an indication for DDD pacing were implanted with the short tip-ring electrode. Another 23 patients received the conventional electrode. FFRW and P-wave amplitudes during pacing and intrinsic ventricular depolarization were measured at implantation. Measurements were repeated before hospital discharge and at follow-up between 10 and 14 days after implantation.Results
P-wave amplitude was slightly smaller in the short tip-ring group (2.71 ± 1.04 vs 3.17 ± 1.30 mV in the conventional group, respectively, P = NS). All P-waves exceeded 1.2 mV. FFRW during pacing was 0.07 ± 0.05 in the short tip-ring group and 0.54 ± 0.32 mV in the conventional group (P < 0.001). FFRW during intrinsic rhythm was 0.08 ± 0.04 and 0.55 ± 0.31 mV, respectively (P < 0.001). The ratio between P-wave and FFRW was 48.6 ± 27.2 in the short tip-ring group and 7.3 ± 4.4 in the conventional group (P < 0.001). FFRW and P-wave amplitudes did not change at hospital discharge or during follow-up.Conclusion
FFRW can be suppressed without compromising P-wave sensing by using a pacing electrode with a short tip-ring distance. Whether reduced FFRW amplitude results in clinical endpoints remains to be determined.