Comparing the Efficacy and Safety of a Novel Monophasic Waveform Delivered by the Passive Implantable Atrial Defibrillator With Biphasic Waveforms in Cardioversion of Atrial Fibrillation

Background-: The passive implantable atrial defibrillator (PIAD) (with no battery or discharging capacitor and powered transcutaneously by radio-frequency energy) delivering a novel monophasic low-tilt waveform is more efficacious than the standard monophasic waveform at atrial defibrillation. Standard biphasic (STB) waveforms, however, are more efficacious and safer than monophasic waveforms. This study compared the efficacy and safety of the PIAD waveform with biphasic waveforms. Methods and Results-: Sustained atrial fibrillation (AF) was induced by rapid atrial pacing. Cardioversion was attempted via 2 atrial defibrillation leads. The efficacy of the PIAD was compared with 3 biphasic waveforms (standard, single rounded, and double rounded) at varying voltage settings in 10 pigs. After a synchronized shock, hemodynamic changes between the PIAD, standard biphasic, and monophasic waveforms were compared at 1.5 and 3.0 J in 12 pigs. Myocardial injury (biochemical and histological) after ten 5-J PIAD shocks was compared with a no-shock group in 14 pigs. The PIAD 100-V setting was significantly more efficacious than the STB (100/-50 V: 100% [1.88+/-0.02 J] versus 90% [0.89+/-0.0 J]; P =0.025). No arrhythmic, hemodynamic, or myocardial injury was observed with the PIAD waveform. Conclusions-: Defibrillation with the PIAD is more efficacious than with the STB waveform and appears safe. This device could provide a more effective option for cardioversion. (C) 2004 American Heart Association, Inc.; References: 1. Manoharan G, Evans N, Kidwai B, et al. A novel passive implantable atrial defibrillator using transcutaneous radio frequency energy transmission successfully cardioverts atrial fibrillation. Circulation. 2003; 108: 1382-1388. 2. Cooper RAS, Johnson EE, Wharton M. Internal atrial defibrillation in humans: improved efficacy of the biphasic waveforms and the importance of phase duration. Circulation. 1997; 95: 1487-1496. 3. Tomassoni G, Newby KH, Kearney MM, et al. Testing different biphasic waveforms and capacitances: effect on atrial defibrillation threshold and pain perception. J Am Coll Cardiol. 1996; 28: 695-699. 4. Harbinson MT, Allen JD, Imam Z, et al. Rounded biphasic waveform reduces energy requirements for transvenous catheter cardioversion of atrial fibrillation and flutter. Pacing Clin Electrophysiol. 1997; 20 (pt II): 226-229. 5. Kidwai BJ, Allen DJ, Harbinson MT, et al. Waveform optimisation for internal atrial defibrillation: effects of waveform rounding, phase duration and voltage swing. Pacing Clin Electrophysiol. 2001; 24: 1198-1207. 6. Tang W, Weil MH, Sun S, et al. The effects of biphasic and conventional monophasic defibrillation on postresuscitation myocardial function. J Am Coll Cardiol. 1999; 34: 815-822. 7. Leng CT, Paradis NA, Calkins H, et al. Resuscitation after prolonged ventricular fibrillation with use of monophasic and biphasic waveform pulses for external defibrillation. Circulation. 2000; 101: 2968-2974. 8. Guyton AC, Hall JE. Textbook of Medical Physiology: Cardiac Arrhythmias and Their Electrocardiographic Interpretation. 9th ed. Philadelphia, Pa: WB Saunders; 1996: 149-158. 9. Kerber RE, Martins JB, Gascho JA, et al. Effects of direct-current countershocks on regional myocardial contractility and perfusion: experimental studies. Circulation. 1981; 63: 323-332. 10. Feng Y-J, Chen C, Fallon JT, et al. Comparison of cardiac troponin I, creatine kinase-MB and myoglobin for detection of acute ischemic myocardial injury in a swine model. Am J Clin Pathol. 1998; 110: 70-77. 11. Merin RG. Myocardial Metabolism, Cardiac Anaesthesia (Volume 2): Cardiovascular Pharmacology. Kaplan JA, ed. New York, NY: Grune & Stratton; 1983: 253-254. 12. Trouton TG, Allen JD, Yong LK, et al. Metabolic changes and mitochondrial dysfunction early following transthoracic countershock in dogs. Pacing Clin Electrophysiol. 1989; 12: 1827-1834. 13. Coltorti F, Bardy GH, Reichenbach D, et al. Effects of varying electrode configuration with catheter-mediated defibrillator pulses at the coronary sinus orifice in dogs. Circulation. 1986; 73: 1321-1333. 14. Bardy GH, Allen MD, Mehra R, et al. Transvenous defibrillation in humans via the coronary sinus. Circulation. 1990; 81: 1252-1259.