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  • Poster presentation
  • Open Access

Biphasic DC shock as a first-line therapy in recent-onset stable atrial fibrillation in the emergency department

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  • 1 and
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Critical Care200711 (Suppl 2) :P220

  • Published:


  • Atrial Fibrillation
  • Emergency Department
  • Midazolam
  • Sinus Rhythm
  • Antiarrhythmic Drug


To evaluate the efficacy of early electric cardioversion (EC) with a biphasic defibrillator and the impact on atrial function in recent-onset atrial fibrillation (AF).


The study population consisted of 21 consecutive patients (mean age 58 years; range 35–76 years) with AF lasting from less than 48 hours. Hemodynamically stable AF was treated via DC shock if sinus rhythm (SR) was not restored in 6 hours after i.v. antiarrhythmic drug therapy. All patients were pretreated with heparin 5,000 U i.v. The defibrillator used was the Heartstart MRX using a biphasic waveform and low energy (70–120 J). A trans-thoracic echo was performed pre-EC and 1 hour post-EC. All patients were sedated with midazolam (in vivo titolation). Atrial function (ejection fraction, surface area, A wave) and ventricular function (ejection fraction) were evaluated. The patients returned to the emergency department after 7 days for follow-up. Data were analyzed using descriptive statistics (Table 1).
Table 1





Number of patients



Age average



Sinusal rhythm restoration



Left atrial ejection fraction two chambers



35 (P = 0.02)

Left atrial ejection fraction four chambers



35 (P = 0.02)

Left ventricular ejection fraction



54 (P = NS)

A wave (m/s)




DC shock was successful for all patients (100%) and in 19/21(90.4%) at first shock. There was a significant increase in atrial function with the reappearance of the A wave. There were no thromboembolic complications. After 7 days, results showed that 19/21 (90.4%) patients were in SR.


Early electric cardioversion in the emergency department setting is a simple technique that allows the restoration of SR without complications. The biphasic waveform uses lower energy with a positive impact on atrial function. Higher energy can cause transient tissue damage due to electroporation that can affect the outcome of defibrillation therapy being both pro-arrhythmic and anti-arrhythmic. The recovery of atrial function is also due to the short duration of arrhythmia. The early cardioversion avoids atrial remodelling and allows a longer duration of SR.

Authors’ Affiliations

Hospital Sao Paulo, Napoli, Italy


© BioMed Central Ltd. 2007