Pericardial influence on internal defibrillation energy requirements

Abstract

There is no consensus regarding optimal positioning of patch leads for implantation of automatic implantable cardioverter defibrillators. We compared the energy (in joules) required for 50% and 80% successful termination of ventricular fibrillation with titanium-mesh patch leads outside intact normal pericardium and directly on the epicardium in 13 open-chest dogs. Talc was then instilled into the pericardial space to stimulate adhesion formation and pericardial thickening. After 3 weeks of recovery, thoracotomy and defibrillation testing were repeated in nine dogs with the patch leads outside the thickened, adherent pericardium. There were no significant differences in defibrillation energy requirements between locations (p greater than 0.10). In addition, a comparison of electrical impedance measurements at 10 joules showed no significant differences (p greater than 0.30). In this animal model, defibrillation energy requirements were not altered by positioning the patch leads outside normal intact pericardium rather than placing them directly on the epicardium. Furthermore, thickened, adherent pericardium interposed between the patch leads and the heart does not increase defibrillation energy requirements. These data suggest that placement of automatic implantable cardioverter defibrillator patch leads outside the pericardium in patients (including those with pericardial adhesions from previous cardiac operations) will not adversely affect defibrillation efficacy and thus can simplify the implantation procedure.