Editorial Comment concerning “Early Out-of-Hospital Experience with an Impedance-Compensating Low-Energy Biphasic Waveform Automatic External Defibrillator” (White RD)

Cardiac arrest is an all too common problem; it is estimated that 300,000 episodes per year of sudden cardiac death occur in the United States. Two thirds of these patients die before reaching the hospital. Field-recorded electrocardiograms in patients who experience out-of-hospital cardiac arrest reveal a variety of rhythms, including ventricular ~brillation, asystole, electromechanical dissociation, and others. Of these, ventricular ~brillation is the “survivable” rhythm, provided de~brillation is accomplished quickly. The survival rate from other rhythms is almost zero, probably indicating that these rhythms are encountered in extremely damaged hearts. In recent years it has become overwhelmingly evident that the success of resuscitation is critically determined by the time to de~brillation. Prompt de~brillation yields a high success rate. The development of automatic external de~brillators, easy-to-use, accurate, effective units requiring minimal operator training, markedly facilitates out-of-hospital de~brillation. AEDs have become the preferred strategy for ~rst responders in many communities. In turn, this has led to the concept of public access de~brillation, de~brillation by nontraditional responders with minimal training using widely available AEDs, preplaced in areas where large numbers of people congregate: hotels, airport terminals, convention centers, etc. This concept envisions AEDs being made available and used in much the same way as ~re extinguishers: preplaced on the wall, available for use by individuals with appropriate but not extensive training. A parallel development has been the use of biphasic waveforms for de~brillation. Electrophysiologists have recognized for many years that biphasic waveforms are more effective than monophasic waveforms when used in automatic implantable cardiovertorde~brillator (AICD) units, and such waveforms are now standard for AICDs. More recently, such waveforms have been shown to be more effective than standard monophasic waveforms for transthoracic de~brillation in studies carried out in hospital settings, such as the operating room. Combining biphasic waveforms with AEDs could result in smaller, lighter, and cheaper AEDs, a highly desirable development for the widespread use of these units. However, published reports to date have only studied the use of biphasic waveform transthoracic de~brillation within hospitals. Will biphasic waveforms be as effective in the prehospital environment, characterized by longer response times? The paper by White in the present issue is the ~rst report of biphasic waveform AEDs used in out-of-hospital cardiac arrest. Using a device that adjusts waveform duration based on impedance, White reports the results of 18 patients treated for prehospital arrest. Eight of these patients were not in ventricular ~brillation, and the device appropriately did not advise or deliver shocks to these patients. Ten patients were in ventricular ~brillation (VF); the arrhythmia was correctly recognized in all of these patients and shocks were delivered. Fifty-one VF episodes in these patients were terminated with a total of 62 shocks (1.2 shocks per patient). More than one shock was needed in only nine episodes, and the maximum number of shocks required to de~brillate was three. This is a very favorable and exciting initial report. However, several important cautions and questions remain: (1) The number of patients is very small, as emphasized by the authors. Many more patients need to be studied. Further, such studies need to be done using a randomized controlled design (biphasic vs. traditional monophasic waveforms). (2) Although the ef~cacy of VF termination was 100% using biphasic waveforms, in other ways the results are disappointing. Five of the patients had unwitnessed arrests, and none of these even had spontaneous circulation restored. In the 5 witnessed arrests, despite a response time of 6.6 6 1.7 minutes, only 3 of 5 had spontaneous circulation restored and only one survived to discharge home. The message here is that biphasic waveforms in AEDs are not a panacea. Response times remain critical and need to be even shorter. A more effective waveform will not Journal of Interventional Cardiac Electrophysiology 1997;1:209–210 © Kluwer Academic Publishers. Boston. Printed in U.S.A.