The 64 pole basket catheter used for the mapping procedure will be defined "atypical" sites which sustain atrial fibrillation. The ablation through the driver will lead to more rapid ablation of the atrial fibrillation.

Atrial fibrillation (AF) is a common abnormal and rapid heart rhythm characterized by erratic electrical activity of the upper chambers of the heart. This cardiac arrhythmia may lead to stroke, heart failure, low blood pressure, chest pain, and increased mortality rate. Treatment may include medication to stop the rhythm abnormality, blood thinners, and/or ablation. Ablation involves application of heat or freezing to the area sustaining the rhythm abnormality. This requires tubes (catheters)to be placed in the heart. Human atrial fibrillation may be sustained by localized drivers (rapid and/or organized sites of atrial electrical activation). By mapping/recording the patient's specific atrial anatomy and atrial electrical activity with the 64-pole basket catheter, we may add to the knowledge base of these driver locations. We may also add to the knowledge about where best to ablate to terminate the arrhythmia. Typical anatomic

Inclusion Criteria:

• Patients at VCU Medical Center who are 21 years or older undergoing EPS for ablation of persistent AF (non-rheumatic) whose AF episodes last equal to or greater than 7 days but terminate with DC cardioversion or anti-arrhythmic drugs and do not recur within 24 hours.
• Per current standard of care, AF patients must have failed equal to or greater than 1 anti-arrhythmic drug to qualify for ablation.

Exclusion Criteria:

• Active coronary ischemic in the past year
• Rheumatic valve disease, that leads to distinct AF and increases thromboembolic risk
• Prior ablation or cardiac surgery, that alters atrial electophysiology
• Left atrial clot or dense contrast on TEE, which would increase thromboembolic risk
• Out of range serum electrolytes, including K outside 4.0-5.0 mmol/1
• Left atrial diameter greater than 60 mm, to exclude extreme structural remodeling and failure to maintain sinus rhythm
• Thrombotic disease, venous filters, transient ischemic attack or cerebrovascular accident, to minimize additional risk
• Pregnancy
• Inability or unwillingness to provide informed consent
• Unable to converse in English
• Use of anti-arrhythmic drug less than 5 X half-life Prior ablation or cardiac surgery, that alters atrial electophysiology

48 patients with persistent AF, 7=longstanding AF, 23 paroxysmal AF