Dual Shock Versus Single Shock Synchronized External Direct Current Cardioversion for Atrial Fibrillation - A Double-blinded Randomized Trial

Patient Enrollment Patient enrollment will be open enrollment to inpatient/outpatients who meet the inclusion/exclusion criteria listed above. This is a double-blinded study with randomization to dual shock or standard single shock synchronized cardioversion for patients requiring cardioversion for atrial fibrillation. Randomization will be performed using a standard computer-based randomization system.

Cardioversion will be performed with Zoll R series Defibrillator, which was approved by the FDA in 2017 for use as a defibrillator, with a 510K approval for use in cardioversion of atrial arrhythmias. After obtaining consent, before sedation is administered, all patients will have 2 pads placed in the antero-posterior pad position on the left chest (guideline recommended position for cardioversion of atrial fibrillation) and an additional 2 pads placed in the standard Ventricular Tachycardia/Advanced Cardiac Life Support positions, where the anterior pad is centered over the right infraclavicular space and the apical pad is placed over the left axilla . All patients will be sedated using propofol administered by anesthesiology or a combination of fentanyl and midazolam administered by cardiology staff.

Patients randomized to single shock will then be treated initially with a 200 Joule shock through the antero-posterior pads only. A repeat attempt will be made using the same approach if the initial shock fails. If the second attempt fails, the single shock approach will be considered to have failed. Patients will be crossed over to dual shock therapy while under the same sedation episode. For cross-over patients, two near-simultaneous 200-Joule shocks will be delivered through the two sets of pads already in position. If this fails further treatment will be determined by the primary team/attending cardiologist.

Patients randomized to the dual shock group will have two near-simultaneous 200-Joule shocks delivered through the two sets of pads (antero-posterior position and right infraclavicular-axillary position). The first of these shocks will be synchronized. If the first attempt with this approach fails to terminate atrial fibrillation a second attempt will be made using the same approach. If the second attempt fails the dual shock approach will be considered to have failed and further treatment will be determined by the primary team/attending cardiologist.

Primary Endpoint - Successful termination of atrial fibrillation after initial Direct Current Ccardioversion (DCCV). Successful cardioversion = immediate termination of atrial fibrillation with electrocardiographic (ECG) evidence of atrial fibrillation (AF) termination. The physician deciding whether AF was successfully terminated will be blinded to whether the shock was with single or dual shocks. - Partial success will be considered if atrial fibrillation is terminated by the second attempt using the same approach. Secondary Endpoints - Maintenance of normal sinus rhythm at one hour post cardioversion - Presence of symptomatic skin burn (symptoms rated on a scale of 1-10) - Thromboembolic complications - Ventricular Arrhythmias requiring additional shock therapy Documentation of Anticoagulation All patients need to have established therapeutic anticoagulation. Either 1) Therapeutic warfarin (with International normalized ratio (INR) >2) or therapeutic doses of apixaban, dabigatran, rivaroxaban or edoxaban for at least 3 consecutive weeks before and with plans to continue 4 weeks after cardioversion. 2) Therapeutic anticoagulation with intravenous heparin or therapeutic subcutaneous enoxaparin or non-vitamin K oral anticoagulant if atrial fibrillation episode is known to be of recent onset (<48 hours), with anticoagulation to continue for at least one week post cardioversion. 3) Sub-therapeutic or no anticoagulation preceding cardioversion, but transesophageal echocardiogram (TEE) confirming absence of intra-cardiac thrombus. Therapeutic anticoagulation should be administered just prior to cardioversion and planned to continue for at least 4 weeks post cardioversion.