A RANDOMIZED CONTROLLED CLINICAL-STUDY TO QUANTIFY THE EFFECT OF SMALL CHANGES IN THE DESIGN OF PACING ELECTRODES ON THRESHOLD VOLTAGES

A double-blind randomized study of three pacing leads, identical in al l ways except for the surface of their electrodes, is presented. The l eads were implanted in 30 patients. Ten patients (Group A) received a standard Laserdish lead (dish electrode with laser pores), 10 patients (Group B) received a platinum-iridium coated modified Laserdish elect rode, and 10 patients (Group C) received a platinum-iridium coated dis h electrode identical to that in Group B except for the absence of las er pores. All leads were implanted by the same operator via the subcla vian vein and all patients received an Optima MPT pulse generator. Dir ect measurement at implantation of pacing threshold and endocardial el ectrograms showed no significant difference between the three groups ( mean +/- standard deviation voltage thresholds 0.30 +/- 0.06 V at 0.5 ms and 0.21 +/- 0.05 V at 1.0-ms pulse durations, R wave amplitude 7.6 +/- 3.2 mV). Significant differences (P = 0.001) were found in thresh old impedances at implant (Group A 940 Ohm, Group B 782 Ohm, Group C 6 73 Ohm). Ten further measurements of voltage threshold were made over the next 2 years. Overall, at a pulse duration of 1.0 ms, a significan tly reduced (P < 0.025) threshold voltage was found for both the elect rode with pores and platinum-iridium coating compared with pores alone (20%), and with pores and platinum-iridium coating compared with the coating alone (18%). There was no significant difference between using platinum-iridium alone or pores alone. We have shown that a controlle d randomized study, using electrodes that are identical except for the characteristics being assessed, can enable effects of small differenc es in electrode design to be quantified.