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Increased defibrillation threshold with right-sided active pectoral can
P R Roberts1, S Allen, T Betts
1Department of Electrophysiology, Wessex Cardiothoracic Centre, Southampton University Hospitals, United Kingdom.
Unlabelled:
The aim of this study was to identify the optimal position on the chest wall to place an implant able cardioverter defibrillator in a two-electrode system, consisting of a right ventricular electrode and active can.
Methods And Results:
Defibrillation thresholds (DFT) were measured in 10 anaesthetised pigs (weight 33-45 kg). An Angeflextrade mark lead was introduced transvenously to the right ventricular apex. The test-can (43 cc) was implanted submuscularly in each of four locations: left pectoral (LP), right pectoral (RP), left lateral (LL) and apex (A). The sequence in which the four locations were tested was randomized. Ventricular fibrillation (VF) was induced using 60 Hz alternating current. Rectangular biphasic shocks were delivered 10 seconds after VF induction. The DFT was measured using a modified four-reversal binary search. The results of the four configurations were: LP, 14.6+/- 4.0 J; RP, 18.8+/- 4.2 J; LL, 14.7+/- 4.1 J; A, 14.9+/- 3.1 J. Repeated measures analysis of variance showed that the DFT of RP was significantly higher than LP, LL and A (p < 0.05).
Conclusions:
Implanting an active can in the RP position increases the DFT by 29% compared to LP, LL and A sites. The can position on the left thorax does not appear to have a significant influence on DFT.