Position of Epicardial Patch Electrodes for Implantable Defibrillation Significantly Affects Shock Strength Requirements
Article first published online: 29 SEP 2008
© 1995 Society for Academic Emergency Medicine
Academic Emergency Medicine
Volume 2, Issue 1, pages 50–55, January 1995
How to Cite
Knight, B. H. K., Heil, J. E., Hahn, S. J. and Lang, D. J. (1995), Position of Epicardial Patch Electrodes for Implantable Defibrillation Significantly Affects Shock Strength Requirements. Academic Emergency Medicine, 2: 50–55. doi: 10.1111/j.1553-2712.1995.tb03083.x
- Issue published online: 29 SEP 2008
- Article first published online: 29 SEP 2008
- Received: October 7, 1993 Revision received: December 1, 1993 Accepted: December 4, 1993
- ventricular fibrillation;
- epicardial electrodes;
- ventricular tachycardia
Objective: To assess the impact of epicardial patch electrode position on internal defibrillation efficacy.
Methods: Two mesh patch electrodes (13 cm2) were positioned on the epicardium of acute, isoflurane- anesthetized pigs (n = 7, 40–47 kg). Defibrillation efficacy was determined for three different patch positions: P1 = anterior-basal right ventricle (RV) and lateral-apical left ventricle (LV); P2 = lateral RV and lateral LV; and P3 = anterior-basal septal region and posterior-apical septal region. To quantify defibrillation efficacy, single capacitor discharge, fixed-tilt (68%) biphasic waveforms were delivered to the heart 10 seconds after initiation of ventricular fibrillation. Initial shock intensities were selected using an up/down protocol. Conversion data were used to construct sigmoidal curves relating probability of defibrillation to energy delivered, peak voltage, and peak current in each animal.
Results: Mean peak voltage and current at 50% defibrillation probability were 40% higher for P2 than they were for either P1 or P3 (p < 0.05). Similarly, mean energy delivered was 75% higher for P2. In this pig model, position of epicardial patch electrodes affects defibrillation efficacy.
Conclusion: Apical-to-basal shock vectors (P1 and P3) yielded significantly lower defibrillation shock strength requirements than did a lateral-wall-to-lateral-wall vector (P2), which was perpendicular to the intraventricular septum. These data may help explain the disparity in defibrillation thresholds observed in the human population of patients undergoing implantable cardioverter defibrillator testing with epicardial patch electrodes.