Results and Conclusions. Ibutilide increased DFT (161.1 +/- 33.3 J vs. 200 +/- 54.8 J, p = 0.044). Ibutilide did not significantly change any other variable measured. The ITV did not significantly change any variable measured. Ibutilide appears inactive in the pig, while the ITV may not function properly when used with automatic ventilators.Objectives. Class III antiarrhythmics have been demonstrated to lower defibrillation threshold (DFT). The impedance threshold valve (ITV) has been demonstrated to improve hemodynamics during cardiopulmonary resuscitation (CPR). We hypothesize that administration of the class III antiarrhythmic drug ibutilide, and use of the ITV during CPR after induction of ventricular fibrillation (VF) will lead to greater short-term survival vs. control.Methods. VF was induced in 30--35 kg pigs and left untreated for 4 minutes. CPR was performed for 8 minutes using automatic ventilation. 0.005 mg/kg IV ibutilide was administered during CPR. Electrophysiologic and hemodynamic variables were measured at baseline, during CPR, and post-resuscitation.