Electrical storm and implanted defibrillators.

To the Editor: As more patients obtain automatic implantable cardioverter defibrillators (AICDs), EMS personnel and emergency medical centers will be required to treat the unique situations that such patients present to emergency center personnel. One unique presentation is electrical storm (multiple temporally related episodes of ventricular tachycardia or ventricular fibrillation) (1,2) with an appropriately functioning AICD. (3)

A 65-year-old female was brought to the emergency center by EMS. She was complaining of repeated discharges of her defibrillator, and she complained her chest was hurting because of the discharges. When she arrived, the patient had no IV established, as the EMS personnel were getting shocked while attempting to start an IV. The patient remained conscious throughout her EMS transport and emergency department stay. She had counted many (30) discharges by the time of arrival. She was immediately connected to a cardiac monitor and vital signs were noted: irregular rapid pulse of 160 to 200. Emergency department nurses attempted to establish IV lines but kept getting "shocked" when the patient's defibrillator discharged. The nurses were very concerned that they would be unable to get IV access. However, cardiac monitor observations showed that it took about a 4 second continuous run of ventricular tachycardia/ventricular fibrillation (VT/VF) viewed on the cardiac monitor to trigger the patient's AICD to discharge in about 2 seconds. One to three second runs of VT/VF that self-terminated would not trigger a discharge. By careful observation of the cardiac monitor, nurses could obtain adequate warning as to when to stop physical contact with the patient and avoid a "shock." This practice worked well as the nurses were no longer "shocked" and in a few minutes, IV lines were established and blood was drawn. This was not a trivial success because without vascular access, and with staff too nervous and concerned to establish access, the ability to adequately provide care could have been compromised.

Conventional lidocane therapy was followed by a 300 mg amiodarone bolus and drip (1 mg/min). This treatment markedly reduced the VT/VF runs and allowed the patient to have relief from frequent AICD discharges. This allowed time to get a more complete history from the patient, discover and treat her underlying causes for her electrical storm (low potassium and medical noncompliance).

With increasing numbers of patients obtaining AICDs, EMS and emergency center personnel need to have a working knowledge of how to handle patients that present with symptoms in which AICDs play a role. Being shocked from a patient's AICD discharge is at best startling and at worst could cause fear in some caregivers that could compromise patient care. Discharges felt while touching a patient's skin are not strong enough to cause fibrillation in caregivers. (4) However, even with this knowledge, it is difficult to do procedures with confidence if a caregiver is frequently and randomly shocked while attempting a procedure. In this case, we describe an easy method to avoid getting shocked, which our caregivers found to be very valuable. Simply observing the cardiac monitor for VT/VF runs that last about 4 seconds will allow a caregiver about 2 seconds of warning before the AICD discharges. No caregiver was shocked once we used this method; confidence was reestablished and IV lines were started.

Although the use of lidocane was done in this case with some effectiveness, switching to amioderone was the key for suppressing the patient's VT/VF. Electrical storm has been successfully treated by various medications. (5) Currently, amioderone seems to be the most effective. (5)

Electrical storm in patients with an appropriately discharging AICD can be a medical emergency that challenges caregivers in unique ways. Both the patient and caregivers can obtain successful resolution of the problems of repeated AICD discharges if the caregivers proceed with knowledge of the discharge cycle of the AICD. Consequently, caregivers can avoid getting shocked. If the caregivers are inadvertently shocked, they know that the shock is unlikely to cause them harm. Patients then can have the underlying causes for the electrical storm determined and therapy applied to resolve the electrical storm.

Charles P. Davis, MD, PhD

Division of Emergency Medicine

Department of Surgery

University of Texas Health Science Center at San Antonio 

Department of Emergency Medicine

Texsan Heart Hospital

San Antonio, TX

References

1. A comparison of antiarrhythmic-drug therapy with implantable defibrillators in patients resuscitated from near-fatal ventricular arrhythmias. The Antiarrhythmics versus Implantable Defibrillators (AVID) Investigators. N Engl J Med 1997;337:1576-1583.

2. Kuck KH, Cappato R, Siebels J, et al. Randomized comparison of antiarrhythmic drug therapy with implantable defibrillators in patients resuscitated from cardiac arrest: the Cardiac Arrest Study Hamburg (CASH). Circulation 2000;102:748-754.

3. Exner DV, Pinski SL, Wyse DG, et al. Electrical storm presages nonsudden death: the antiarrhythmics versus implantable defibrillators (AVID) trial. Circulation 2001;103:2066-2071.

4. Peters W, Kowallik P, Reisberg M, et al. Body surface potentials during discharge of the implantable cardioverter defibrillator. J Cardiovasc Electrophysiol 1998;9:491-497.

5. Connolly SJ, Dorian P, Roberts RS, et al. Comparison of beta-blockers, amiodarone plus beta-blockers, or sotalol for prevention of shocks from implantable cardioverter defibrillators: the OPTIC Study: a randomized trial. JAMA 2006;295:165-171.