Case Report

Double-dose external cardioversion for refractory unstable atrial fibrillation in the ED

Abstract

A 45-year-old man with dilated cardiomyopathy, atrial fibrillation, and hypertension presented to the emergency department with palpitations and shortness of breath for 2 days after running out of his medications. An electro- cardiogram disclosed atrial fibrillation with rapid ventricular response. The patient was hemodynamically unstable and failed multiple cardioversion attempts up to 360 J. A second defibrillator was then attached and the patient successfully cardioverted once both defibrillators were set to their maximum levels, thus delivering a total of 720 J. Double- dose external cardioversion with 2 defibrillators is an important alternative method that the emergency physician should be aware of when treating refractory atrial fibrillation in the hemodynamically unstable patient.

Atrial fibrillation with rapid ventricular response is a common presentation in the emergency department (ED). Hemodynamically unstable AF requires emergent external synchronized cardioversion, which is unsuccessful in up to 43% of patients [1]. The simultaneous use of 2 defibrillators has been shown to successfully cardiovert refractory AF in stable patients [2-5]; however, this technique has not been described in the unstable patient with a rapid ventricular response in an emergent setting. We describe a case of a hemodynamically unstable patient presenting to the ED with rapid AF resistant to conventional cardioversion. Sinus rhythm was restored through the use of 2 defibrillators discharged simultaneously to deliver a total of 720 J.

A 45-year-old man with dilated cardiomyopathy, AF, and hypertension presented to the ED with palpitations for 2 days. He complained of shortness of breath but denied chest pain.

On physical examination, he was afebrile; his pulse was 185 beats per minute, blood pressure 88/70 mm Hg, respi- ratory rate 40 breaths per minute, and oxygen saturation 92% on room air, which improved to 100% on a non- rebreather mask. He was a large man who was visibly tachypneic and diaphoretic. He had jugular venous disten- sion to the angle of his jaw, inspiratory rales involving

three quarters of his lungs bilaterally, and minimal Lower extremity edema.

A rhythm strip and electrocardiogram disclosed AF with rapid ventricular response (see Fig. 1). The patient soon became hypotensive with systolic blood pressures in the range of 60 to 70 mm Hg despite the initiation of a 250 mL bolus of normal saline. Standard defibrillator pads were placed in an anterior-posterior orientation, and the patient was synchronously shocked with 100 J without success. Because his systolic blood pressure rose to more than 100 mm Hg, 1 mg of midazolam and 50 ug of fentanyl were given intravenously, and cardioversion was reattempted at 200 J. This and a subsequent third attempt at 360 J also failed to cardiovert the patient. Intravenous doses of furosemide (80 mg), digoxin (0.5 mg), and amiodarone (150 mg) were then administered.

Because the patient’s hemodynamic status remained tenuous, pads of a second defibrillator were placed in an anterolateral configuration. After receiving additional doses of midazolam and fentanyl, high-energy cardioversion was performed by 2 operators, simultaneously pressing the discharge buttons on the 2 defibrillators. Although the first attempt at 600 J failed, the patient successfully converted once both defibrillators were set to their maximum levels, thus delivering a total of 720 J. His vital signs stabilized and his electrocardiogram demonstrated restoration of sinus rhythm without an injury pattern. A chest radiograph showed massive cardiomegaly and pulmonary edema.

The patient’s maximum creatine kinase level was 2313 (reference range, 22-269), with a creatine kinase-MB fraction of 7.5 and index of 0.3. He had 3 negative troponin I values less than 0.030. He did not develop any other complications as a result of the defibrillations.

According to the American College of Cardiology guidelines, hemodynamically unstable AF, which is marked by hypotension, myocardial ischemia, or congestive heart failure, requires emergent synchronized cardioversion [6]. However, standard cardioversion fails to induce sinus rhythm in up to 43% of patients [1].

There is no protocol for patients with unstable AF who fail cardioversion. Patients with stable AF who fail external cardioversion are usually treated with Rate control or attempts at internal or transesophageal cardioversion [2]. However, rate control may worsen already unstable patients

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385.e2 Case Report

Fig. 1 Initial electrocardiogram disclosing atrial fibrillation with rapid ventricular response.

whose tenuous blood pressure prohibits the use of ? blockers and calcium channel blockers [7]. Furthermore, intracardiac and transesophageal cardioversion are invasive and not readily available in the ED [3,8]. Double-dose external cardioversion (also known as high-energy or quadruple-pad cardioversion) offers one possible solution to this predicament [2-5].

Failure of standard cardioversion is usually due to inadequate current being delivered to the heart [9]. This inadequacy usually results from high transthoracic impe- dance from obesity, musculature, or pulmonary disease [2,5,9]. The energy from double-dose external shocks, first described for refractory ventricular arrhythmias in 1994, surmounts this impedance [10]. The additional paddles may be placed adjacently anteroposterior or in the apex-anterior or apex-posterior position [2,3,5,10,11].

The risks of double defibrillation include clot emboliza- tion, body cramps, skin burns, transient bundle-branch blocks, and postcardioversion Sinus bradycardia [2-4].

Data for high-dose cardioversion are from monophasic defibrillators, which have been the standard for decades. More data are needed to evaluate the incidence of AF refractory to biphasic waveforms and the use of biphasic double-dose external cardioversion [12].

To date, all studies examining this technique have been performed in Hemodynamically stable patients who have had AF for a minimum of 1 month [2-5]. The case presented is unique in that it demonstrates the success of double-dose shocks in a hemodynamically unstable patient with rapid AF in the ED setting. Double-dose external cardioversion with 2

defibrillators is an important alternative method that the emergency physician should be aware of.

Andrew K. Chang MD Gretchen S. Lent MD Diana Grinberg MD

Department of Emergency Medicine Albert Einstein College of Medicine Montefiore Medical Center

Bronx, NY 10467, USA

E-mail address: achang@montefiore.org doi:10.1016/j.ajem.2007.07.024

References

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2. Saliba W, Juratli N, Chung MK, et al. Higher energy synchronized external direct current cardioversion for refractory atrial fibrillation. J Am Coll Cardiol 1999;34:2031-4.
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5. Kabukcu M, Demircioglu F, Yanik E, et al. Simultaneous double external DC shock technique for refractory atrial fibrillation in concomitant heart disease. Jpn Heart J 2004;45:929-36.

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