Clinical paperA randomised controlled trial of the effect of biphasic or monophasic waveform on the incidence and severity of cutaneous burns following external direct current cardioversion☆
Introduction
We have shown previously that elective direct current (DC) cardioversion causes cutaneous burns as quantified by erythema index, skin temperature and hyperalgesia measured using Von Frey hairs.1 Pain is also common after this procedure, with 84% of patients experiencing some degree of pain and 23% experiencing moderate to severe pain at 2 and/or 24 h after the procedure. The severity of burns were found to correlate with the number and total energy of shocks delivered.1
Successful cardioversion requires the passage of a transthoracic current of sufficient magnitude to depolarise a critical mass of myocardium and restore sinus rhythm. Because of the high resistance across the thorax, a relatively high amount of energy is required to deliver sufficient current density. Protocols using a monophasic waveform discharge up to 360 J, equating to 30–50 A2 and approximately 3000 V.3 Although the time course of this shock is only 5–10 ms, the energy is sufficient to cause superficial burns to the skin. Damage may result from both thermal heating4 as a result of the high impedance at the electrode-skin interface, and electroporation of the cell membrane caused by high current density.5
Compared with monophasic waveforms, biphasic waveforms require less energy and current flow in DC defibrillation3, 6, 7, 8 and cardioversion9, 10, 11 to achieve equal or superior efficacy. Thus pain and inflammation after the procedure, which has been shown previously to correlate with the number and total energy of monophasic shocks delivered, might be expected to be less after biphasic cardioversion. However, although one study which incorporated a cross-over element to its design measured pain using a visual analogue scale (VAS)11 and another (which also incorporated a cross-over element to its design) used a subjective four point scale to document “dermal injury”, to our knowledge, there have been no previous detailed randomised studies of the effects of biphasic or monophasic waveform on pain and inflammation secondary to DC cardioversion. We therefore designed a prospective randomised double-blinded controlled study of patients undergoing elective DC cardioversion to compare the incidence and severity of burns using monophasic or biphasic waveforms.
Section snippets
Materials and methods
Following approval by the local Research Ethics Committee, informed written consent was obtained from 139 sequential adult patients (18 years of age or above) scheduled to undergo elective DC cardioversion. There were no exclusions other than refusal to participate in the study. Patients were randomised by a separate blinded investigator using random number generator software (www.randomizer.org) and sealed envelopes to receive either biphasic (70, 100, 150, 200, and 300 J) or monophasic (100,
Results
We prospectively obtained consent from 139 patients. Subsequently, 11 patients were withdrawn or withdrew after consent had been gained (see Table 1). We obtained complete results from 128 patients (93 male). Median age was 70 (22–87) years, weight 83.0 (42.0–139) kg, mean body mass index (BMI) 28.2 ± 4.50 kg m−2 and median TTI 81.5 (49.0–158) Ω. Prior to cardioversion, atrial fibrillation was present in 110 patients while atrial flutter was present in 18 patients. The numbers of shocks applied to
Discussion
This study found that patients who received a biphasic waveform for elective DC cardioversion of atrial arrhythmias experienced less pain as measured by visual analogue scale at two and 24 h after the procedure, compared with patients who received a monophasic waveform. There was also a reduction in erythema index at the edge of the sternal pad sites in those patients who received a biphasic waveform.
The number needed to treat indicates that on average, eight patients need to be treated with
Conclusions
The use of a biphasic waveform for DC cardioversion reduces the inflammation and pain of burns as measured by erythema index and visual analogue scale. On average, eight patients need to be treated with biphasic rather than monophasic cardioversion to reduce one patient's pain at 2 h from moderate or severe to mild or none.
Conflict of Interest Statement
We received a grant and the loan of the PIC biphasic defibrillator for the duration of the study from Welch-Allyn MRL inc. as above.
Acknowledgements
We thank Dr David A Zideman and Dr John A Prickett for their help and advice with this study.
This study was supported by unrestricted grants from Welch-Allyn MRL inc, Wessex Heartbeat (Southampton University Hospital NHS Trust) and the Association of Anaesthetists of Great Britain and Ireland.
References (28)
- et al.
The incidence and severity of cutaneous burns following external DC cardioversion
Resuscitation
(2004) The defibrillator and cardiac burns
J Thorac Cardiovasc Surg
(1963)- et al.
Comparison of a novel rectilinear biphasic waveform with a damped sine wave monophasic waveform for transthoracic ventricular defibrillation. ZOLL Investigators
J Am Coll Cardiol
(1999) - et al.
A comparison of biphasic and monophasic shocks for external defibrillation. Physio-Control Biphasic Investigators
Prehosp Emerg Care
(2000) - et al.
Biphasic transthoracic defibrillation causes fewer ECG ST-segment changes after shock
Ann Emerg Med
(1997) - et al.
High perimeter impedance defibrillation electrodes reduce skin burns in transthoracic cardioversion
Am J Cardiol
(1998) - et al.
Nature and determinants of skin “burns” after transthoracic cardioversion
Am J Cardiol
(1997) - et al.
Time course of primary and secondary hyperalgesia after heat injury to the skin
Br J Anaesth
(1993) - et al.
Topical ketorolac has no antinociceptive or anti-inflammatory effect in thermal injury
Burns
(1994) - et al.
Topical glucocorticoid has no antinociceptive or anti-inflammatory effect in thermal injury
Br J Anaesth
(1994)
Hyperalgesia in a human model of acute inflammatory pain: a methodological study
Pain
The visual analogue pain intensity scale: what is moderate pain in millimetres?
Pain
The effect of topical non-steroidal anti-inflammatory cream on the incidence and severity of cutaneous burns following external DC cardioversion
Resuscitation
Determining the optimal paddle force for external defibrillation
Am J Cardiol
Cited by (0)
- ☆
A Spanish translated version of the summary of this article appears as Appendix in the online version at doi:10.1016/j.resuscitation.2006.04.014.