Patient outcomes following defibrillation with a low energy biphasic truncated exponential waveform in out-of-hospital cardiac arrest
Introduction
In several previous publications, we have reported our experience with community-wide early defibrillation employing a dual police/paramedic response [1], [2], [3], [4], [5]. Our primary end-point in two of these studies was patient outcome, with secondary outcomes of call-to-shock time interval and restoration of spontaneous circulation with shocks only (ROSC patients), as opposed to those who needed advanced life support interventions (ALS patients). In one of these reports, we described the evolution of post-defibrillation cardiac rhythms in patients treated with monophasic damped sine (MDS) shocks and those defibrillated with impedance-compensated biphasic truncated exponential (BTE) shocks [4]. In December 1996, we introduced BTE waveform automated external defibrillators (AEDs) into our early defibrillation program and in 1997 reported our early experience with this waveform in the termination of ventricular fibrillation (VF) in ten patients with long-duration VF, only five of whom had sustained a witnessed arrest [5]. The purpose of this report is to present our experience with patient outcome in witnessed VF arrest after the introduction of defibrillation with this non-escalating low-energy waveform.
Section snippets
Materials and methods
We have described our materials and methods in detail [1], [2], [3], [4], [5]. In December 1996, 12 BTE AEDs (ForeRunner®, Agilent Technologies/Heartstream Operation, Seattle, WA) were placed in police cars and four in ambulances. In early 1998, the ambulance AEDs were transferred to fire vehicles and two additional units were placed in these vehicles, thus making 18 BTE AEDs available in police cars and fire vehicles. During the BTE AED study period, the population and area of the city
Results
During the study period, 42 patients in VF when first encountered by police, firefighters or paramedics were treated with BTE shocks. Of the 42 patients, 31 (74%) regained a sustained spontaneous circulation on-scene and 16/42 (38%) survived to discharge. Four patients were outside the City of Rochester, but within the area for which our emergency medical services (EMS) system is the ALS response. In these communities, the same BTE AED was used by first responders. Of the 42 patients with VF,
Discussion
While we have shown in previous publications [4], [5], [6], [8] a high rate of termination of VF with non-escalating low-energy shocks (150 J), patient outcome data have not been assessed rigorously in our EMS system since deployment of this waveform. Our program has provided an opportunity to assess patient outcome after defibrillation with low-energy BTE shocks and to retrospectively compare patient outcomes in patients treated with escalating high-energy MDS shocks. The results indicate that
Conclusions
These data indicate that our high rates of discharge survival over several years’ experience with rapid defibrillation in a community-wide setting were sustained when non-escalating low-energy BTE waveform shocks were deployed. Defibrillation was achieved with high-efficacy even in the presence of long-standing underlying coronary heart disease with previous CABG and/or PTCA, valvular heart disease and dilated cardiomyopathy. If energy-related myocardial dysfunction has clinical relevance, then
Acknowledgements
We thank Kimberly Sankey for assistance with the manuscript; City of Rochester Police and Fire Departments; Gold Cross Ambulance Service; and law enforcement and ambulance dispatch personnel.
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