927-33 Maturation of an Atrial Defibrillation Lead System Causes No Change in Threshold

Previous work in transvenous ventricular defibrillation has shown changes in defibrillation requirements during lead maturation. We evaluated the changes in atrial defibrillation thresholds for a three lead transvenous system over a three month period.In 8 adult sheep (60±10kg at implant), a three-lead atrial defibrillation system was implanted. Two custom built atrial defibrillation leads, each with a 6cm distal shocking coil, were positioned. one in the great cardiac vein and one in the right atrium. A bipolar pacing lead was positioned at the right ventricular apex for shock synchronization. Leads were connected to data blocks which were inserted into subcutaneous pockets. Custom insulated needles were inserted through the skin and into the datablocks to establish electrical contact with the leads. If atrial fibrillation was stable, an atrial defibrillation threshold (ADFT)was obtained at implant and at follow-up studies 2, 4, 8, and 12 weeks after implant. ADFTs were obtained in a 10V step-up manner as previously described by our group. The ADFTs from animals with stable AF (N) for each follow-up interval are shown in the table below. Values are mean±1 sd.NADFT-VADFT-EImpedanceImplant5138±40 V0.7±0.4 J56±7 Ω2Wk6125±37 V0.6±0.5 J51±4 Ω4Wk6125±41 V0.6±0.4 J52±3 Ω8Wk5112±29 V0.5±0.2 J61±7 Ω12Wk7145±53 V0.8±06 J63±8 ΩThere was no significant difference in the ADFT voltage or energy over the three month follow-up period (p>0.05). Lead impedance was not significantly different for any of the follow-up intervals as compared to implant (p>0.05) however weeks 2 and 4 were significantly lower than weeks 8 and 12 (p<0.05)Conclusions;Unlike ventricular defibrillation thresholds from transvenous leads, a trial defibrillation thresholds from transvenous leads do not significantly change over the three months after implant