Stable electrical performance of high efficiency pacing leads having small surface, steroid-eluting pacing electrodes

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.