Stable Electrical Performance of High Efficiency Pacing Leads Having Small Surface, Steroid‐Eluting Pacing Electrodes

Abstract

Previous experience with steroid-eluting small electrode designs have described their increased pacing efficiency, yet some reports have questioned their electrical stability. We report our experience with a new pacing lead design incorporating small surface (i.e. 1.2 mm2), high impedance pacing electrodes. Medtronic Model 5034 ventricular pacing leads were implanted by a single physician in 167 patients. Of those, 96 patients had an additional Model 5534 atrial lead implanted. All patients were followed for at least 9 months. Microdislodgment, as defined by a sudden increase in pacing threshold accompanied by radiographic stability, was observed in 6 of 263 (2.3%) leads implanted. Of the 4/167 (2.4%) ventricular leads that exhibited electrical instability, only 2 were sustained. Importantly, neither was significant enough to result in loss of capture. The other two cases of ventricular electrode instability manifested as a transient threshold rise with eventual return to near the original values. By comparison, the atrial lead model exhibited a sudden and sustained pacing threshold rise 5 which was evident in two patients (2.1%) with neither requiring invasive intervention. For all remaining chronic leads, clinically acceptable electrical performance profiles were demonstrated. We conclude that low microdislodgment rates and stable electrical performance profiles can be achieved with the small electrode steroid-eluting pacing electrodes as long as careful lead positioning and securing techniques are followed during implantation. We further suggest that successful high impedance lead design is critically dependent on its stiffness and mass characteristics.

1‐Year Performance of a Defibrillation Lead with a Small Electrode Surface for High Impedance Pacing: A Randomized, Controlled Study

“…The electrode surface area is inversely related to the pacing impedance, and high impedance pacing leads with small surface electrodes have recently been shown to extend the estimated generator longevity without compromising overall system performance. 13,[17][18][19] The use of a defibrillation lead with a small electrode tip surface for high impedance pacing might, therefore, enhance ICD longevity in selected patients. However, due to the critical role of the defibrillation lead for appropriate device function and for the patient's life, its overall performance should be carefully assessed.…”

“…At the same time, pacing thresholds were not different in the two lead models. Considering the existing experience with high impedance pacing leads, 13,[17][18][19] it thus seems likely that defibrillation leads with a small electrode tip surface will decrease energy consumption and prolong device longevity, especially in ICD patients with a high percentage of ventricular pacing.…”

“…Although tip designs are not identical to the lead model 6944, recently published studies conducted in larger pacemaker patient populations are in line with the findings of the present study, also demonstrating stable electrical performance of small surface, steroid-eluting pacing electrodes. [17][18][19]…”

Microdislodgment:

“…However, there were also some reports of a higher incidence of a sudden pacing threshold rise of the CapSure Z ventricular leads 2 , 7 . The incidence of sudden pacing threshold rise of those leads thought to be due to microdislodgment varied from 2.2% to 11.2%, 1 , 3 , 5 , 7 while that of the CapSure SP ventricular leads (Medtronic Inc.) with 5.8 mm 2 surface area was lower, <2% in prior reports 5 , 7 , 10 . Deshmukh et al 1 thought that the variability in results of the CapSure Z ventricular leads may be related to a greater sensitivity of the small electrode design to subtle changes at the electrode to tissue interface.…”

“…High impedance has been achieved by reducing the pacing electrode surface area (1.2 mm 2 ) while maintaining high conductivity within the lead body, thereby maintaining the voltage delivered to the electrode tissue interface. Furthermore, the newer small surface, porous platinum electrode incorporating steroid‐elution has demonstrated a favorable electrical performance profile equivalent to the traditional larger surface electrode 1–6 . However, sudden pacing threshold rise immediately after implantation have been demonstrated in some reports of CapSure Z leads 2 , 7 …”