Modification of the detection and stimulation behavior of active and passive fixed bipolar pacemaker electrodes by depot dexamethasone

: In a prospective, non-randomised study, two atrial steroid-eluting screw-in leads were evaluated (CapSureFix 4068, Medtronic, n = 17; Accufix II DEC 033-812, Telectronics, n = 16); in the same way, measurements were obtained of three steroid eluting ventricular electrodes (two screw-in leads: CapSureFix 4068, Medtronic, n = 11; Accufix II DEC 033-212, Telectronics, n = 20 and one tined lead Encor DEC 033-448, Telectronics, n = 18). Measurements were performed during implantation (= acute), 7 +/- 3 days after implantation (= subacute) and during follow-up at 3 and 6 months. After atrial implantation, there were no significant differences of the stimulation thresholds (Accufix II DEC: 0.76 +/- 0.23 V-CapSureFix: 0.75 +/- 0.16 V). During follow-up, a slight but not significant increase of the stimulation threshold was observed (Accufix II DEC: subacute 0.99 +/- 0.45 V; 3 months 0.79 +/- 0.43 V; 6 months: 0.84 +/- 0.45 V.-CapSureFix: subacute 0.76 +/- 0.18 V; 3 months 0.87 +/- 0.31 V; 6 months 0.88 +/- 0.32 V). The acute atrial thresholds were significantly lower in the right atrial appendage than in the right lateral wall, while there was no difference during measurements at 3 and 6 months (atrial appendage n = 20 acute 0.69 +/- 0.11 V; right lateral wall n = 13 acute 0.85 +/- 0.25 V). The ventricular Encor DEC and Accufix II DEC electrodes had similar thresholds at implantation, whereas the CapSureFix electrode showed significantly higher stimulation thresholds (Encor DEC 0.56 +/- 0.15 V; Accufix II DEC 0.53 +/- 0.13 V; CapSureFix 0.8 +/- 0.16 V). During follow-up the stimulation threshold increased significantly with each ventricular electrode (Encor DEC: subacute 0.71 +/- 0.22 V; 3 months 0.77 +/- 0.23 V; 6 months 0.8 +/- 0.28 V-Accufix II DEC: subacute 0.86 +/- 0.44 V; 3 months 0.8 +/- 0.25 V; 6 months 0.74 +/- 0.21 V-CapSureFix: subacute 0.92 +/- 0.17 V; 3 months 1.14 +/- 0.46 V; 6 months 1.12 +/- 0.32 V). With regard to the sensing of the intracardiac signals, no differences among the electrodes were detected at the atrial as well as the ventricular level. Subacutely all electrodes had a significant decrease of sensing level without changes after 3 and 6 months (atrium: CapSureFix acute 4.08 +/- 1.34 mV, subacute 3.09 +/- 0.88 mV, 3 months 2.91 +/- 1.02 mV, 6 months 3.0 +/- 1.22 mV; Accufix II DEC acute 4.34 +/- 1.49 mV, subacute 2.86 +/- 1.18 mV, 3 months 3.07 +/- 1.04 mV, 6 months 2.91 +/- 1.16 mV-ventricle: CapSureFix acute 11.55 +/- 4.5 mV, subacute 9.99 +/- 3.51 mV, 3 months 9.36 +/- 3.23 mV, 6 months 9.13 +/- 3.4 mV; Accufix II DEC acute 10.66 +/- 3.0 mV, subacute 7.49 +/- 4.04 mV, 3 months 7.25 +/- 3.64 mV, 6 months 7.52 +/- 4.1 mV; Encor DEC acute 11.65 +/- 3.9 mV, subacute 9.04 +/- 3.29 mV, 3 months 8.69 +/- 3.83 mV, 6 months 8.78 +/- 3.32 mV). The impedance of the Accufix II DEC electrode was significantly lower than the CapSureFix electrode at the time of implantation in the atrium. The ventricular electrodes with active fixation showed a decrease of impedance 7 days after implantation, which diminished during chronic follow-up. On the other hand, the Encor DEC electrode did not exhibit any change of impedance at the different times of determination. In summary, the dexamethasone depots prevented the rise of the stimulation threshold in all the atrial electrodes with active fixation. There remained a small increase of the stimulation threshold after ventricular implantation, which did not reach clinical significance. Thus, the energy saving output of 2.5 volt could be programmed in almost every patient.