Waveform optimisation for internal cardioversion of atrial fibrillation

Introduction: A novel atrial defibrillator was developed at the Royal Victoria Hospital in collaboration with the Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster. This device is powered by an external pulse of radiofrequency (RF) energy and designed to cardiovert using low tilt monophasic (LTMW) and low tilt biphasic waveform (LTBW), 12 ms pulse width. This study compared the safety and efficacy of LTMW with LTBW for transvenous cardioversion of atrial fibrillation (AF).Methods: Patients with persistent AF and with previous history of failed external cardioversion were randomised to LTMW or LTBW. Warfarin INR level was maintained in between 2-3 for 4 weeks prior cardioversion. St Jude’s defibrillating catheter was positioned in the distal coronary sinus and right atrium and connected to the defibrillator via a junction box. After a test shock using a dummy load, patient was cardioverted in a step up progression from 50V to 300V. Shock success was defined as return of sinus rhythm for >/=30 seconds. If cardioversion was unsuccessful at peak voltage patient was crossed over to the other arm of waveform type and cardioverted at peak voltage. Results: Thirty patients (50%) were equally randomised to LTBW and LTMW. Seven out of 15 (46%) cardioverted to sinus rhythm with LTBW and 1/15 (6%) with LTMW (p