Unipolar ventricular pacing reduces inappropriate shocks from a separate cardioverter defibrillator in a post-Fontan patient.

This report describes a 20-year-old man with complex congenital heart disease and inappropriate epicardial implantable cardioverter defibrillator (ICD) shocks secondary to double counting of ventricular-paced spikes and QRS complexes from a separate bipolar epicardial dual-chamber pacemaker. Adjusting to a unipolar paced-ventricular mode resolved any double counting via pacemaker-ICD interaction.