Current of injury predicts acute performance of catheter-delivered active fixation pacing leads.

BACKGROUND

During pacemaker lead (PPML) implantation, the implanter must assess lead stability (fixation) and pacing threshold adequacy. Implanters rely principally on lead impedance (IMP) and pacing threshold measurements after fixation of the PPML to determine adequacy of pacing sites. Continuously monitoring lead parameters during fixation might better identify predictors of acute lead stability and performance.

METHODS

At the time of PPML implantation with a catheter delivered, fixed screw, 4-Fr PPML (Medtronic 3830, Minneapolis, MN, USA) patients underwent measurements of R-wave amplitude, slew rate, and current of injury (COI) (maximum and at 80 ms) during each turn of the helix. Lead stability was tested with traction applied to the lead body.

RESULTS

Eighteen patients (age 70 +/- 9 years, 9 males) were studied. Right ventricular lead positioning was attempted 43 times; 26 positions demonstrated good fixation and 18 had satisfactory threshold. Sites of good fixation consistently showed larger COI (maximum and at 80 ms) compared to poor fixation sites throughout each turn of the helix; R wave, slew rate, and IMP did not differ significantly. When all measures of COI were examined in a stepwise regression model only the final measure of COI at 80 ms proved significantly associated with acute stability (P = 0.032).

CONCLUSIONS

Lead stability and threshold adequacy are predictable from assessment of the magnitude of injury current. Continuous monitoring of lead parameters during fixation does not appear to confer any benefit over assessment of the parameters after final rotation of the lead. A negative COI is associated with poor threshold and/or fixation.