Waveform optimization for internal cardioversion of atrial fibrillation Vivek Kodoth, MBBS, MRCP (UK), a Noel C. Castro, BSc, MSc, b Ben M. Glover, MB BCh, MD, MRCP (UK), a Jim M. Anderson, BSc, MPhil, PhD, c Omar J. Escalona, BSc, MSC, PhD, c Ernest Lau, MB BCh, MD, MRCP (UK), a Ganesh Manoharan, MB BCh, MD, FRCP (UK) a,c, ⁎ a The Heart Centre, Royal Victoria Hospital, Belfast, Northern Ireland b Departamento de Electronica, Universidad Simon Bolivar, Caracas, Venezuela c Centre for Advanced Cardiovascular Research, University of Ulster, Newtownabbey, UK Received 16 June 2011 Abstract Introduction: A novel atrial defibrillator was developed at the Royal Victoria Hospital in collaboration with the Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster. This device is powered by an external pulse of radiofrequency energy and designed to cardiovert using low-tilt monophasic waveform (LTMW) and low-tilt biphasic waveform (LTBW), 12 milliseconds pulse width. This study compared the safety and efficacy of LTMW with LTBW for transvenous cardioversion of atrial fibrillation (AF). Methods: Patients were anticoagulated with warfarin to maintain International Normalized Ratio between 2 and 3 for 4 weeks prior cardioversion. Warfarin international normalized ratio level was maintained in between 2 and 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, the patient was cardioverted in a step-up progression from 50 to 300 V. Shock success was defined as return of sinus rhythm for 30 seconds or more. If cardioversion was unsuccessful at peak voltage, the patient was crossed over to the other arm of the waveform type and cardioverted at peak voltage. Results: Thirty patients were randomized equally to LTBW and LTMW (15 each). Seven out of 15 patients (46%) cardioverted to sinus rhythm with LTBW, and 1 (6%) of 15, with LTMW (P = .035). Including crossover patients, 14 patients (46%) converted to sinus rhythm. After crossover, 4 patients were cardioverted with LTBW and 2 with LTMW. Overall mean voltage, current, and energy used for cardioversion were 270.53 ± 35.96 V, 3.68 ± 0.80 A, and 9.12 ± 3.73 J, respectively, and intracardiac impedance was 70.82 ± 13.46 Ω. For patients who were successfully cardioverted, mean voltage, current, energy, and intracardiac impedance were 268.28 ± 42.41 V, 3.52 ± 0.63 A, 8.51 ± 3.16 J, and 73.92 ± 12.01 Ω. There were no major adverse complications during the study. Cardiac markers measured postcardioversion were unremarkable. Conclusion: Low-tilt biphasic waveform was more efficacious for low-energy transvenous cardioversion of AF. A significant proportion of patients were successfully cardioverted to sinus rhythm with low energy. Radiofrequency-powered defibrillation can be safely used for transvenous cardioversion of AF. © 2011 Elsevier Inc. All rights reserved. Introduction Atrial fibrillation (AF) is a chaotic breakdown of electrical activity in the upper chamber of the heart. It is the most common sustained arrhythmia seen in clinical practice and is responsible for substantial morbidity and mortality. The incidence and prevalence of AF increases with age. The prevalence of AF roughly doubles with each decade, from 0.5% at age 50 to 59 years to almost 9.0% at age 80 to 90 years. 1 Atrial fibrillation accounts for 30% to 40% of all hospitalizations because of arrhythmias. Atrial fibrillation is a complex disease process, and the manage- ment of AF should be tailored to the individual patient after considering the underlying heart disease and its interactions Available online at www.sciencedirect.com Journal of Electrocardiology 44 (2011) 689 – 693 www.jecgonline.com ⁎ Corresponding author. The Heart Centre, Royal Victoria Hospital, Grosvenor Road, Belfast, UK. E-mail address: gmanoharan@msn.com 0022-0736/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jelectrocard.2011.08.008