927-32 Effects of Digoxin and Sotalol on Atrial Defibrillation Thresholds via Implanted Transvenous Catheter Electrodes

Objectives It has been documented in animal models that a synchronized shock delivered to the atria through transvenous catheter electrodes is a feasible method to terminate atrial fibrillation (AF). Because digoxin and sotalol are frequently used in the management of patients with AF, we studied the effect of these drugs on atrial defibrillation thresholds (ADFTs). Methods Sterile pericarditis was created using standard methods in 17 mongrel dogs. Two catheter electrodes with a 6 cm coil tip were inserted through the right external jugular vein and placed in the distal coronary sinus and in the right atrial appendage, respectively. They were subsequently used for delivery of atrial shocks. On the second postoperative day, AF was induced by rapid atrial pacing, and ADFT was determined in the drug free state and after administration of 1) a therapeutic dose of digoxin (50 μg/kg; 6 dogs); 21 a toxic dose of digoxin (increased dose, mean 106 μg/kg, associated with a digitalis toxic rhythm; 6 dogs); or 3) sotalol (1 mg/kg followed by a continuous infusion of 0.375 mg/kg/hr; 5 dogs). ADFT was determined in a 10 V step-up manner, with 20 shocks delivered at the lowest intensity that converted AF to determine % success. ADFT was defined as the lowest defibrillation energy which achieved successful atrial defibrillation between 10% and 90% of the time. Results Data are shown in mean ± SD. Digoxin Voltage (V) Energy (J) Impedance (Ω) %Success (%) Drug free 85 ± 21 0.27 ± 15 40 ± 7 40 ± 17 Therapeutic dose 77 ± 29 0.28 ± 18 36 ± 3 30 ± 19 Toxic dose 77 ± 29 029 ± 0.16 36 ± 8 42 ± 16 Sotalol Drug free 64 ± 5 013 ± 04 45 ± 7 30 ± 23 Sotalol 52 ± 8 * 0.10 ± 03 44 ± 7 29 ± 18 * p l 005 Digoxin did not significantly affect the voltage, energy, or impedance of the shock, butsotalol significantly decreased the mean ADFT voltage required. Conclusions In the sterile pericarditis model of AF: 1) ADFT was very low (1l03 J) through transvenous catheter electrodes; and 2) digoxin did not significantly affect ADFTs, although sotalol decreased ADFTs determined using transvenous catheter electrodes.