Far-field R-wave reduction with a novel lead design: experimental and human results

The purpose of this study was to examine a bipolar screw-in lead (NL), specially designed to reduce unwanted far-field R-wave (FFRW) signal detection in an acute human setting. The results were compared with animal experiments.

The newly designed lead with a center-to-center distance between the anode and cathode electrodes of 3.23 mm, corresponding to an inter-electrode spacing of 1.1 mm was implanted in nine canines with a follow-up of 6 months. Sensing of P waves, FFRW signals, pacing threshold, and impedance was measured at regular intervals. As a result of the positive outcome with the animal study, an acute human experiment was performed. In patients scheduled for conventional dual chamber pacemaker implantation, the NL was compared to a Tendril Model 1388T bipolar screw-in lead (St. Jude Medical, CRMD, Sylmar, CA).

Utilizing a tip-to-ring distance of 1.1 mm, the optimum P wave to FFRW ratio was found in animal experiments. In the acute human tests in 15 patients, the mean P-wave voltage of the 1388T lead of 3.30 +/- 1.54 mV was slightly larger than that of the NL, at 2.55 +/- 1.11 mV, but did not differ significantly (P = 0.13). The FFRW voltage of the 1388T lead was 0.62 +/- 0.37 mV and was significantly greater from that of the NL, at 0.10 +/- 0.08 mV (P < 0.0001). Pacing thresholds and pacing impedances were comparable.

Animal testing results were reproducible in the acute human test setting. The lead reduced the paced FFRW signal amplitudes significantly, allowing for high atrial sensitivity settings but without sensing the FFRW. A robust P-wave signal could be retained.