Author + information
- Received June 17, 1996
- Revision received October 4, 1996
- Accepted December 4, 1996
- Published online March 15, 1997.
- Parwis C Fotuhi, MDA,
- Bruce H KenKnight, MSB,
- Sharon B Melnick, ASC,
- William M Smith, PhDC,
- Gert F Baumann, MDA and
- Raymond E Ideker, MD, PhDC,* ()
- ↵*Dr. Raymond E. Ideker, University of Alabama at Birmingham, Volker Hall, B140, 1670 University Boulevard, Birmingham, Alabama 35294-0019.
Objectives. We investigated the impact of an inactive endocardial lead on the 50% effective dose (ED50%) for successful ventricular defibrillation.
Background. The presence of abandoned epicardial mesh patch electrodes detrimentally affects the defibrillation efficacy of an endocardial lead system. It is not known whether abandoned endocardial electrodes produce a similar effect.
Methods. An endocardial lead system (ENDOTAK, model 0062, Cardiac Pacemakers, Inc.) was implanted in eight dogs (mean ±SD weight 23.7 ± 1.0 kg). The ED50% for each of seven lead configurations was determined by a three-reversal point protocol in a balanced-randomized order with and without a second electrically passive endocardial lead system in the right ventricle (power 0.97 to detect a 50-V difference). Biphasic shocks with 80% tilt were delivered 10 s after the induction of ventricular fibrillation. In one configuration the active electrode made contact with the passive electrode in the right ventricular (RV) apex. In another configuration the active electrode was placed in a more proximal position to avoid contact. Additionally, the ED50% was determined for the endocardial lead system with a passive pacing lead positioned in the RV apex.
Results. ED50% values for peak voltage, peak current and delivered energy were not significantly different with or without a passive RV electrode, and this was true whether or not the active electrode touched the passive electrode. However, ED50% values were significantly higher when the active electrode was slightly proximal than when it was positioned at the apex.
Conclusions. Physical contact between active and passive endocardial electrodes does not significantly alter defibrillation efficacy in this dog model. An increase in ED50% energy was caused by a slightly proximal position. Therefore, a good electrode position within the right ventricle is a more important determinant of defibrillation efficacy than is avoidance of the electrode touching a passive electrode.
(J Am Coll Cardiol 1997;29:825–30)
☆ This study was supported in part by Research Grant HL-42760 from the National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland; Grant CDR-8622201 from Duke University National Science Foundation Engineering Research Center, Durham, North Carolina; and by Guidant Corporation, Indianapolis, Indiana and Physio-Control Corporation, Redmond, Washington; and was presented in part at the 68th Annual Scientific Sessions of the American Heart Association, Anaheim, California, November 1995 and the 62nd Jahrestagung der Deutschen Gesellschaft für Kardiologie, Mannheim, Germany. Drs. Ideker and Smith have consulting agreements with Cardiac Pacemakers, Inc., a division of Guidant Corporation.
- Received June 17, 1996.
- Revision received October 4, 1996.
- Accepted December 4, 1996.
- The American College of Cardiology