CLINICAL-EXPERIENCE WITH A NEW LEAD COMBINING ACTIVE FIXATION WITH STEROID ELUTION

The Medtronic lead engineering model number 10335A represents a new co ncept in lead design combining active fixation with steroid elution. I t aims for immediate stability and low chronic thresh olds. Twenty-one leads, 9 atrial and 12 ventricular, were implanted in 13 patients (10 males, mean age 68; range 22-91 years). The atrial leads showed no ri se in pulse width threshold at a voltage of 1.6 volts (mean thresholds at implant, 1, and 26 weeks; 0.1 +/- 0.09 msec, 0.15 +/- 0.04 msec, a nd 0.1 +/- 0.03 msec, respectively). The ventricular leads had a small but significant rise between implant and 1 week at an output of 1.6 v olts (0.07 +/- 0.03 msec increasing to 0.11 +/- 0.04 msec; P < 0.02) b ut no significant later rise (0.1 +/- 0.04 msec at 2 weeks and 0.1 +/- 0.05 msec at 6 months). These low chronic thresholds would allow earl y reprogramming of the unit to low voltages resulting in a battery sav ing with prolongation of the unit's life. There were no significant ch anges in the P and R wave amplitudes, but there was a fall in lead imp edance in the ventricular leads between implantation and 2 week (P < 0 .02) but none subsequently, and there was no significant change in atr ial impedance. There were no sensing failures and no lead displacement s. Despite impressive pacing characteristics, the study was suspended because of a high level of mechanical complications. Of the 96 patient s implanted worldwide with 136 leads there were eight helix deformatio ns, which will require redesign. However, the concept of steroid eluti on combined with active fixation appears to be an attractive and valid concept and is supported by this data; further studies are planned.