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Medical Devices

Energy Levels in External Biphasic Defibrillators: Initial FDA Safety Communication

Date: November 5, 2009

Clinical community and specific health care professionals including Electrophysiology Labs, code teams, Cardiac Catheterization Labs, Operating Rooms, Intensive Care Units, Emergency Rooms, Risk Managers, Quality Managers, Patient Safety Coordinators, Directors of Nursing, Medical Directors, Biomedical/Clinical engineers, Emergency Medical Services

Professional Organizations, including the American Heart Association, American College of Cardiology, Heart Rhythm Society, American Hospital Association, American Nurses Association, American Medical Association, and Electrophysiology physicians

Medical Specialty: Cardiology

Devices: External biphasic defibrillators that deliver energy levels ≤ 200 Joules (J), including monitor/defibrillators and automated external defibrillators (AEDs).

Summary of Problem and Scope
FDA is investigating energy levels in external biphasic defibrillators with shocks ≤ 200 J. We have received reports of 14 events since 2006 in which a 200 J biphasic defibrillator was ineffective in providing defibrillation/cardioversion therapy to a patient, whereas a subsequent shock from a different 360 J biphasic defibrillator resulted in immediate defibrillation/cardioversion. The majority of events occurred during attempts at cardioversion of atrial fibrillation, but there was at least one instance with defibrillation of a ventricular arrhythmia as well. FDA is seeking additional information in order to interpret the significance of these events, and to determine whether FDA activities are advised.

If you experience an event similar to those reported above, we encourage you to report to the FDA as outlined below under Reporting Problems.

So far, our analysis of the 14 cases does NOT suggest the need for any change to current clinical practice. As FDA continues its evaluation of this situation, we encourage you to follow the American Heart Association’s guidelines/algorithms for treatment of cardiac arrhythmias, and to follow manufacturers’ instructions for using defibrillators.

FDA Activities
In addition to reviewing our adverse event report database, FDA has explored the literature on defibrillation effectiveness. We recognize that there are multiple contributors to defibrillation and cardioversion success. Patient attributes, such as the size and shape of a person’s body, presenting rhythm, defibrillator attributes, such as energy level and waveform, and treatment conditions such as drug therapy and oxygenation, all affect defibrillation and cardioversion outcomes.

Although the reports received by FDA (cited above) involve multiple shocks from defibrillators from different manufacturers on a single patient, FDA is also aware that the scientific literature does not provide clarity on this question of optimal energy delivery. The only randomized trial known to us comparing effects of different energy levels focused on patients with cardiac arrest, in contrast to the reports received by FDA that primarily relate to atrial arrhythmias. In that trial, patients were randomized to fixed energy delivery (150 J even if multiple shocks were required) or escalating energy delivery (200, then 300 and finally 360 J, if multiple shocks were required). Although escalating energy levels resulted in a greater proportion of successful cardioversion/defibrillation for patients requiring multiple shocks (primarily in those patients in ventricular fibrillation rather than those in ventricular tachycardia), there were no detectable differences in clinical outcomes (survival to 1 hour, to 24 hours or to discharge).1

Reporting Problems
Prompt reporting of adverse events can help FDA identify and better understand the risks associated with medical devices. If you suspect a problem with a defibrillator, such as a situation where a patient received shocks from multiple devices, we encourage you to file a voluntary report through MedWatch, the FDA Safety Information and Adverse Event Reporting program.

Healthcare personnel employed by facilities that are subject to FDA's user facility reporting requirements should follow the reporting procedures established by their facilities.

To help us learn as much as possible about situations in which a patient received shocks from multiple defibrillators, please include the following information in your reports, if available:

  • Energy level/intensity
  • Waveform (biphasic truncated exponential or biphasic rectilinear)
  • Acute vs. chronic cardiac rhythms
  • Drug therapy
  • Oxygenation
  • Paddles vs. pads
  • Delay in therapy
  • Make and model of devices
  • Time from collapse to shock

If you have questions about this communication, please contact the Division of Small Manufacturers, International and Consumer Assistance (DSMICA) at or 800-638-2041.

This document reflects FDA’s current analysis of available information, in keeping with our commitment to inform the public about ongoing safety reviews of medical devices. The nature, magnitude and possible public health impact of this situation are not yet clear.

1 Stiell IG, Walker RG, Nesbitt LP, et al., Circulation. 2007;115:1511-15173

Page Last Updated: 10/06/2014
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