Internal atrial and ventricular defibrillation during electrophysiology procedures.

Over the last twenty years internal defibrillation has evolved from an experimental technique into an important adjunctive procedure in the electrophysiology laboratory. Internal deflbrillation is used for treating persistent atrial fibrillation and refractory ventricular arrhythmias. Atrial defibrillation can be performed with several electrode configurations but generally shocks from 1 to 50 joules are delivered between electrodes placed in the coronary sinus and lateral wall of the right atrium. Ventricular defibrillation is usually performed with electrodes in the right ventricle and superior vena cava, although "unipolar" configurations with an internal ventricular electrode and a skin electrode can be used. Currently, internal deflbrillation can be required in 5-10% of cases within the electrophysiology laboratory and will become more commonly used as electrophysiologists perform more complex catheter ablation procedures.