ABSTRACT
The Medtronic lead engineering model number 10335A represents a new concept in lead design combining active fixation with steroid elution. It aims for immediate stability and low chronic thresholds. 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 rise 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, and 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 volts (0.07 +/- 0.03 msec increasing to 0.11 +/- 0.04 msec; P < 0.02) but 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 early reprogramming of the unit to low voltages resulting in a battery saving with prolongation of the unit's life. There were no significant changes in the P and R wave amplitudes, but there was a fall in lead impedance in the ventricular leads between implantation and 1 week (P < 0.02) but none subsequently, and there was no significant change in atrial impedance. There were no sensing failures and no lead displacements. Despite impressive pacing characteristics, the study was suspended because of a high level of mechanical complications. Of the 96 patients implanted worldwide with 136 leads there were eight helix deformations, which will require redesign.(ABSTRACT TRUNCATED AT 250 WORDS)
