Improved chronic epicardial pacing in children: steroid contribution to porous platinized electrodes

Although new "low threshold" epicardial electrodes combine steroid with a porous, platinized-platinum surface, the actual contribution of steroid elution has not been established. We evaluated this new electrode surface design with and without steroid in 13 children, ages 1-22 years. Both electrodes are unipolar and of similar surface area. The Medtronic Model 4951-P is a barb design for epimyocardial insertion without steroid while the Model 10295A is a steroid eluting, epicardial disk-shaped design. Both electrodes were implanted for atrial and ventricular pacing. At implant, sensed P and R waves, and pacing impedances were comparable between both electrodes. There were no significant differences between initial measured pulse width or calculated energy thresholds for the first 2 months following implant. Strength-duration curves for both electrodes at 1 month were comparable to implant values. After 2 months, the threshold of the nonsteroid electrode peaked and stabilized at a significantly higher (P less than 0.05) level than the more constant steroid eluting electrode. This difference continued for the first year following implant. We conclude that the new porous, platinized-platinum electrode design intrinsically limits initial electrode-tissue interface reactivity in children and improves epicardial pacing with low chronic threshold values. Steroid elution augments these intrinsic qualities by maintaining fibrous capsule stability with more constant low thresholds over time.