Elsevier

Resuscitation

Volume 59, Issue 2, November 2003, Pages 189-196
Resuscitation

Defibrillation waveform and post-shock rhythm in out-of-hospital ventricular fibrillation cardiac arrest

https://doi.org/10.1016/S0300-9572(03)00183-7Get rights and content

Abstract

Background: The importance of the defibrillation waveform on the evolving post-shock cardiac rhythm is uncertain. The primary objective of this study was to evaluate cardiac rhythms following the first defibrillation shock, comparing biphasic truncated exponential (BTE), monophasic damped sinusoidal (MDS), and monophasic truncated exponential (MTE) waveforms in patients experiencing out-of-hospital ventricular fibrillation cardiac arrest (OHCA). Methods: We reviewed the automated external defibrillator (AED) and emergency medical services (EMS) records of 366 patients who suffered OHCA and were treated with defibrillation shocks by first-tier emergency responders between 1 January 1999 and 31 August 2002 in King County, Washington. The post first shock rhythms were determined at 5, 10, 20, 30, and 60 s and compared according to defibrillation waveform. Results: The MDS and BTE waveforms were associated with significantly higher frequency of defibrillation than the MTE waveform, though only the BTE association persisted to 30 and 60 s. No difference in defibrillation rates was detected between MDS and BTE waveforms. By 60 s, an organized rhythm was present in a greater proportion for BTE (40.0%) compared with MDS (25.4%, P=0.01) or MTE (26.5%, P=0.07). Conclusion: In this retrospective cohort investigation, MDS and BTE waveforms had higher first shock defibrillation rates than the MTE waveform, while patients treated with the BTE waveform were more likely to develop an organized rhythm within 60 s of the initial shock. The results of this investigation, however, do not provide evidence that these surrogate advantages are important for improving survival. Additional investigation is needed to improve the understanding of the role of waveform and its potential interaction with other clinical factors in order to optimize survival in OHCA.

Sumàrio

Contexto: A importância da onda de desfibrilhação no estabelecimento do ritmo cardı́aco pós choque é incerta. O objectivo principal deste estudo foi avaliar os ritmos cardı́acos após o primeiro choque de desfibrilação, comparando ondas exponenciais bifásicas truncadas (EBT), descarga sinusoidal monofásica (DSM) e exponencial monofásica truncada (EMT) em doentes com paragem cardı́aca extra-hospitalar por fibrilação ventricular (PCEH). Métodos: Fizemos a revisão dos registos dos desfibriladores automáticos externos (DAE) e dos serviços de emergência médica (SEM) de 366 doentes que sofreram PCEH e foram tratados com choques de desfibrilhação em primeira resposta à emergência, de 1 de Janeiro de 1999 e 31 de Agosto de 2002 em King County, Washington. Os ritmos pós primeiro choque foram determinados aos 5, 10, 20, 30 e 60 segundos e comparados segundo a curva de desfibrilação. Resultados: As ondas DSM e EBT estavam associadas com uma frequência de desfibrilhação significativamente mais elevada que a onda EMT, embora apenas a associação da EBT permanecesse válida aos 30 e 60 segundos. Não se detectaram diferenças na taxa de desfibrilhação entre as ondas DSM e BTE. Aos 60 segundos estava presente um ritmo organizado em maior proporção de doentes tratados com onda BTE (40.0%) se comparados com DSM (25.4%, P=0.01) e EMT (26.5%, P=0.07). Conclusão: Nesta investigação retrospectiva estratificada, a onda DSM e EBT obtiveram taxas de desfibrilhação com o primeiro choque maiores que a onda EMT, enquanto os doentes tratados com onda EBT tinham mais probabilidade de desenvolver um ritmo organizado em 60 segundos após o primeiro choque. Os resultados desta investigação contudo não fornecem evidência que estas vantagens preliminares sejam importantes para a melhoria da sobrevida. É necessária investigação adicional para compreender melhor o papel da onda de desfibrilhação e do seu potencial de interacção com outros factores clı́nicos para melhorar a sobrevida em PCEH.

Resumen

Antecedentes: Es incierta la importancia de la forma de onda de desfibrilación en el ritmo desarrollado después de desfibrilar. El objetivo primario de este estudio fue evaluar los ritmos cardı́acos después de la primera descarga desfibriladora, comparando ondas bifásico exponencial truncado (BTE), monofásico sinusoidal dampeado (MDS), y monofásico exponencial truncado (MTE) en pacientes que experimentan paro cardı́aco extrahospitalario (OHCA) por fibrilación ventricular. Métodos: Revisamos los registros de desfibriladores automáticos externos (AEDs) y de servicios de emergencias médicas (EMS) de 366 pacientes de que sufrieron y fueron tratados con descargas de desfibrilación por reanimadores de primera respuesta entre enero 1 de 1999 y el 31 de Agosto de 2002 en King County, Washington. Se determinaron los ritmos después de la primera descarga a los 5, 10, 20, 30, y 60 s y se compararon de acuerdo con la forma de onda de desfibrilación. Resultados: Las ondas MDS y BTE se asociaron con frecuencia de desfibrilación significativamente mas alta que con onda MTE, aunque solo la asociación de BTE persistió a los 30 y 60 segundos. No se detectaron diferencias en las tasas de desfibrilación entre las ondas MDS y BTE. Por los 60 s, habı́a ya un ritmo organizado presente en una gran proporción para BTE (40.0%) comparado con MDS (25.4%, P=0.01) y MTE (26.5%, P=0.07). Conclusión: En este estudio retrospectivo de investigación de cohorte, las ondas MDS y BTE tuvieron mayor tasa de desfibrilación en la primera descarga que la onda MTE, mientras que los pacientes ondas BTE tenı́an mayor probabilidad de desarrollar un ritmo organizado dentro de los 60 segundos de la primera descarga. El resultado de esta investigación, sin embargo, no proporciona evidencia de que estas ventajas sean importantes para mejorar la sobrevida. Se necesita investigación adicional para una mejor comprensión del rol de la forma de onda y de su posible interacción con otros factores clı́nicos para optimizar la sobrevida en OHCA.

Introduction

Out-of-hospital ventricular fibrillation cardiac arrest (OHCA) is one of the most common causes of cardiovascular death in the United States. Prompt defibrillation is the most effective means to resuscitate victims of OHCA [1], [2], [3]. Several different electrical waveforms may be used to achieve defibrillation. Monophasic waveforms deliver current in only one direction between anode and cathode, while biphasic waveforms deliver current of one polarity during the initial phase and then reverse the current's polarity in the second phase. Monophasic or biphasic waveforms may also vary in their individual configuration, having either a truncated exponential or damped sinusoidal shape. Defibrillation waveforms have been well studied in the electrophysiology laboratory in electrically induced ventricular fibrillation (VF), but our understanding of the relative performance of different waveforms in the setting of OHCA is incomplete [4], [5], [6], [7], [8]. In a randomized study of defibrillation in OHCA, an impedance compensating biphasic truncated exponential (BTE) waveform terminated VF more frequently than monophasic waveforms consisting primarily of monophasic truncated exponential (MTE) [9]. However, the defibrillation efficacy of the MTE waveform may be inferior to the monophasic damped sinusoidal (MDS) waveform [10], [11]. Such variability in waveform configuration complicates making comparisons solely on the basis of whether a shock was “biphasic” or “monophasic”. The importance of defibrillation waveform with respect to its effect on the evolving cardiac rhythm after shock, return of spontaneous circulation (ROSC), and eventual patient survival in OHCA is also uncertain.

The primary objective of this study was to evaluate cardiac rhythms following the first defibrillation shock, comparing MDS, MTE, and BTE waveforms in patients experiencing OHCA.

Section snippets

Study design and setting

The investigation was a retrospective cohort study of cardiac arrest patients presenting with an initial rhythm of VF, who were treated with at least one automated external defibrillator (AED) shock by emergency medical services (EMS) first-tier responders prior to arrival or treatment by second-tier EMS responders in King County (excluding Seattle) from 1 January 1999 through 31 August 2002. This area is served by a two-tiered EMS response system with providers who are all trained to identical

Results

A total of 467 patients suffered out-of hospital VF arrest due to heart disease and received at least one shock from an EMS first-tier responder during the study period. Of these cases, 79 were missing electronic or written records and 22 were incomplete due to malfunctions in the recording equipment, leaving 366 cases (78%) for analysis. There were no significant differences between missing and reviewed cases with regard to the distribution of waveforms, patient, or event characteristics (age,

Discussion

In cardiac arrest, VF is the most frequent initial rhythm [17]. The first step in successful resuscitation is defibrillation, whereby the VF rhythm is terminated. Subsequent steps for successful resuscitation require the restoration of an organized rhythm and ROSC. In this retrospective cohort study of VF cardiac arrest patients treated with first-tier EMS defibrillation, the MDS and BTE waveforms were associated with a higher frequency of defibrillation with the first shock or following the

Conclusion

In this retrospective cohort investigation, the MDS and BTE waveforms were associated with significantly greater defibrillation than the MTE waveform. By 60 s following the initial shock, an organized rhythm was present in a greater proportion of BTE patients. No clear differences were observed across the waveforms with regard to the subsequent steps of resuscitation: ROSC and hospital admission. However, a greater proportion of patients receiving initial treatment with MTE defibrillation

Acknowledgements

The authors thank the EMTs, paramedics, and emergency dispatchers of King County, Washington, for their ongoing excellence in the care of cardiac arrest, as well as Linda Becker, Terry Sinclair, Dan Anderson, and James Scappini of King County EMS for their technical assistance, preliminary review, and organization of the AED recordings.

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