This study seeks to determine the efficacy of single coil defibrillation leads for cardioversion of persistent atrial fibrillation.

This study seeks to compare the efficacy of single coil defibrillation leads for the internal cardioversion of atrial fibrillation as compared with cardioversion by external defibrillation pads. It is known that dual coil leads are effective for atrial cardioversion, but the presence of the SVC defibrillation coil allows for selection of shock vector that more reliably incorporates the majority of atrial tissue compared to a single right ventricular lead. For a variety of reasons single coil defibrillation leads are now implanted in the majority of patients requiring placement of implantable cardiac defibrillators, and many of these patient's will later develop atrial fibrillation and potentially require cardioversion. Currently, there is no clear consensus on how to approach cardioversion in these patient's and both external and internal methods are used. Internal cardioversion may be ineffective exposing patient's unnecessarily to repeated shocks and battery depletion. External cardioversion may carry a small risk of damaged to the CIED.

The investigator's goal is to identify patient's referred for cardioversion for atrial fibrillation who also have an implanted cardiac defibrillator with a single coil defibrillation lead and randomize them to either external or internal cardioversion.

Inclusion Criteria:

• greater than 18 years of age
• persistent atrial fibrillation and have been recommended by your primary cardiologist to undergo cardioversion
• have an implantable cardiac defibrillator

Exclusion Criteria:

• over the age of 99
• pregnant
• prisoner