Importance of electrode conductive surface area and edge effects on ventricular defibrillation efficacy.
INTRODUCTION:The role of edge effects and electrode surface area of the right ventricular (RV) transvenous lead (TVL) on defibrillation efficacy is unknown. METHODS AND RESULTS:Defibrillation threshold (DFT) testing was conducted randomly in 12 dogs using ring electrode leads in an RV/SVC (superior vena cava) or RV/SVC/patch system. The leads (RV-4, RV-8t, RV-8, RV-15) had electrode surface areas of 20%, 20%, 40%, and 70%, respectively. A computer model predicted the magnitude of electrode surface current (RV-8t > RV-4 > RV-8 > RV-15) and the potential distribution (PD) at four sites: electrode surface (site a) and at 2 mm (b), 4 mm (c), and 8 mm (d) away from the surface. Despite different near-field PDs (sites a, b, c), PDs were nearly identical at site d. Resistance decreased as the surface area increased. DFT energy for the RV-15 lead was lower than the RV-4 and RV-8t. There was no difference between energy requirements for the RV-15 and RV-8 leads. No difference was found in DFT current for each lead. Comparison of the RV-8t and RV-4 leads showed no difference in DFT energy despite a lower resistance and a greater number of edges. CONCLUSIONS:Increasing the RV TVL surface area lowered the resistance. However, surface area coverages > or = 40% did not lower DFT energy. No significant change in DFT current occurred despite different predicted near-field current densities. PDs were nearly identical 8 mm from the electrode surface. Thus, the far-field current density appears to play a more important role in determining defibrillation success.
Tomassoni, G; Pendekanti, R; Dixon-Tulloch, E; Miner, B; Fain, ES; Hoffmann, DA; Wolf, PD
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