Europace Advance Access published online on June 15, 2007
Europace, doi:10.1093/europace/eum100
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Do daily threshold trend fluctuations of epicardial leads correlate with pacing and sensing characteristics in paediatric patients?
1 Division of Pediatric Cardiology, University Children's Hospital, Steinwiesstrasse 75, 8032 Zurich, Switzerland; 2 Biostatistic Unit, University of Zurich, Zurich, Switzerland; 3 Division of Congenital Cardiovascular Surgery, University Children's Hospital, Zurich, Switzerland
Aims To evaluate whether the magnitude of daily ventricular pacing threshold fluctuations (
fluctuation) in trend graphs of stored diagrams correlate with ventricular threshold and sensing changes over time.
Methods and results A total of 56 children received AutoCapture® devices (St. Jude Medical, Sylmar, CA, USA) connected to steroid-eluting epicardial leads. Maximum lead age at study closure was 12.2 years (median 4.0). Telemetry data and daily fluctuation were obtained every 6 months. Regression slope coefficients and mean values of repeated measurements were calculated for each patient's course. High daily fluctuation correlated with higher pacing thresholds (
= 0.68, P < 0.001), lower impedances ( = –0.38, P = 0.004), and a fluctuation-incline ( = 0.34, P = 0.01) over time. Furthermore, a fluctuation-incline correlated with a pacing threshold-incline ( = 0.34, P = 0.01). No correlation was observed for ventricular sensing. Higher daily fluctuation were observed if lead age was >5 years compared with 
5 years (0.75 vs. 0.55 V @ 0.5 ms, P = 0.028).
Conclusion High amplitudes of daily fluctuation correlate with higher and increasing pacing thresholds and lower impedances. Theoretically, this results from electrode microinstability on the epicardial surface. A decrease of the steroid-eluting potency of the electrode can be hypothesized to cause higher daily fluctuation beyond a lead age of 5 years. Potential implications of marked daily fluctuation are short-term follow-up and lead replacement in the presence of high pacing thresholds.
Key Words: Pacemaker, Threshold tracking, AutoCapture, Epicardial pacing leads, Paediatric
* Corresponding author. Tel: +41 44 2667519; fax: +41 44 2667981. E-mail address: maren.tomaske{at}kispi.unizh.ch
Manuscript submitted 10 February 2007. Accepted after revision 23 April 2007.
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