Long-term results of low energy stimulation: A multicentre study

A multicentre randomised study was performed on 133 patients (pts.) to evaluate the 3 year follow-up results of threshold behaviour and low energy stimulation by comparing steroid eluting electrodes with Target Tip® electrodes as control. Sixty-five pts. were implanted with VVI and 68 pts. with DDD stimulators. Minimum output allowed by the devices was 0.8V (V) for VVI and 2.5V for DDD pacemakers. The main results showed lower threshold values for the steroid eluting electrodes, compared with the platinised lead (Target Tip®). The advantage of steroid eluting electrodes was statistically appreciable born for ventricular leads (lower mean values of all the measurements: at 3, 7 and 21 days at 2 and 6 months, 1, 2 and 3 years after implantation) and for atrial leads (lower mean values in the measurements performed later). We observed that during the three years follow-up the behaviour of the mean thresholds of pulse duration for both chambers was significantly lower in steroid-eluting leads than in the platinised lead. For example, at 3 years of follow-up steroid-eluting leads had 0.22 ± 10ms ventricular threshold at 0.8V compared with 0.39 ± 13ms in the platinised lead (P<0.001). In the atrium, the steroid-eluting lead's 3 year thresholds at 2.5V were 0.072 ± 0.03ms compared with 0.091 ± 0.06ms for the platinised lead (P<0.01). Seventeen pts. with VVI and steroid eluting electrodes were programmed at 1.6V/0.5ms vs five control (p<0.01). The limitation of lack of lower outputs of the DDD pacemakers did not allow a significant difference in the atrium. No significant loss of capture was demonstrated during low energy stimulation either by 24 Holter recording or at clinical controls. In conclusion, steroid eluting electrodes can maintain low stimulation thresholds even after 3 years. This is probably a consequence of the absence of the 'physiological' threshold increase around the third week after implantation. This threshold behaviour allowed the possibility of safe ventricular stimulation at 1.6V, 0.5ms in a relevant number of patients.