Prevention of deterioration of ventricular fibrillation by basic life support during out-of-hospital cardiac arrest
Introduction
The most important predictor of survival after out-of-hospital resuscitation is the presence of ventricular fibrillation (VF) as initially recorded rhythm. However, when time elapses VF will gradually deteriorate into asystole [1] and consequently decrease the chance of survival [2]. In this period there is much to gain by performing basic life support (BLS) [3], [4]. Animal studies [5], [6], [7] suggest that the mechanism of BLS is the maintenance of myocardial blood flow and thus the preservation of myocardial viability. A human study [8] found a relation between myocardial bloodflow and return of spontaneous circulation (ROSC), but did not study the characteristics of VF.
This study investigated more closely the deterioration in time from VF into asystole and the effect of BLS on that transition and on the characteristics of the VF waveform.
Section snippets
Study design
The data for this work were obtained from a community-based study of which the main results were published earlier [9]. Between June 1, 1995 and August 1, 1997 all consecutive out-of-hospital cardiac arrests were recorded. Ethical committees approved the study.
Specially trained research personnel collected data at the scene of the cardiac arrests. All information from the family, bystanders and emergency medical service (EMS) personnel was collected, with particular attention to estimating the
Initial recorded rhythm and BLS
In the 476 patients who received BLS, 313 (66%) had VF as initial recorded rhythm; 70 (15%) had asystole; and 93 (19%) had another rhythm. In the 397 patients who did not receive BLS, in 200 (50%) the initial recorded rhythm was VF; in 79 (20%) it was asystole; and in 118 (30%) it was another rhythm. These three initially recorded rhythms in patients with and without BLS differed significantly, χ2=21.1, 4.1, and 12.2, respectively. Eventually, 88 patients (10%) were discharged alive from the
Discussion
This study showed the magnitude of the effect of BLS on the gradual deterioration of the amplitude of VF into asystole and the decline of survival as a consequence. The likely mechanism is that BLS maintains coronary perfusion sufficiently to preserve myocardial viability, and thus maintains high VF amplitude. Although the amplitude of VF is only an indirect marker of myocardial perfusion, at present it is the best practical measurement of myocardial viability during cardiac arrest.
Weaver [2]
Acknowledgements
We appreciate the dedicated support of all participating research personnel, dispatchers, ambulance and emergency room personnel in the Amsterdam Dispatch region. Supported by grant from The Netherlands Heart Foundation (94.091).
Portuguese Abstract and Keywords
A sobrevida da paragem cardı́aca é melhorada por suporte básico de vida (BLS). Neste estudo analisou-se a relação entre as caracterı́sticas da fibrilação ventricular (VF) e a sobrevida. Num estudo prospectivo de 2 anos foram analisadas paragens cardı́acas extra-hospitalares assistidas e não traumáticas. Foram analisadas com regressão logı́stica as probabilidades de registar VF, assistolia ou outros ritmos em relação com BLS e o tempo decorrido até ao registo. A
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Portuguese Abstract and Keywords
A sobrevida da paragem cardı́aca é melhorada por suporte básico de vida (BLS). Neste estudo analisou-se a relação entre as caracterı́sticas da fibrilação ventricular (VF) e a sobrevida. Num estudo prospectivo de 2 anos foram analisadas paragens cardı́acas extra-hospitalares assistidas e não traumáticas. Foram analisadas com regressão logı́stica as probabilidades de registar VF, assistolia ou outros ritmos em relação com BLS e o tempo decorrido até ao registo. A amplitude e o cruzamento da linha de base na VF foram relacionados com a sobrevida utilizando análise de regressão linear. Em 873 doentes a probabilidade de registar VF diminuı́a em cada minuto que passava com a vı́tima em colapso (OR 0.92, 95% CI 0.89–0.95) e a probabilidade de registar assistolia aumentava (OR 1.13, CI 1.09–1.18). O BLS reduzia significativamente estes valores para a VF (OR 0.97, 95% CI 0.94–0.99) e assistolia (OR 1.09, 95% CI 1.05–1.13). Não se observou este efeito para outros ritmos. A amplitude da VF diminuiu ao longo do tempo, mas significativamente menos nos que receberam BLS do que naqueles a quem não foi feito BLS (p=0.009). A sobrevida diminuiu significativamente com a diminuição da amplitude da VF (OR 0.23 por mV, 95% CI 0.07–0.79) e com a diminuição dos cruzamentos da linha de base (OR 0.80 por cruzamentos de linha por segundo, 95% CI 0.71–0.91). O nosso estudo demonstrou que o BLS e a VF como ritmo inicial, considerados como sendo factores de previsão de base em modelos de sobrevida, não são independentes entre si. A diminuição da amplitude da VF e o aumento da prevalência da assistolia é significativamente atrasada pelo BLS. A previsão da sobrevida apenas pela amplitude e cruzamentos da linha de base da VF é limitada.
Palavras chave: RCP extra-hospitalar; Fibrilação ventricular; Suporte básico de vida
Spanish Abstract and Keywords
La sobrevida del paro cardı́aco mejora con el soporte vital básico(BLS). Este estudio investigó la relación entre las caracterı́sticas de la fibrilación ventricular (VF) y sobrevida. Se evaluaron los paros cardı́acos prehospitalarios no traumáticos presenciados en un estudio prospectivo de dos años. Se analizaron con regresión logı́sticas las probabilidades de registrar VF, ası́stole u otros ritmos en relación con BLS y el tiempo hasta el registro de ritmo. Se relacionaron la amplitud y cruces de la lı́nea de base de la VF con la sobrevida, usando análisis de regresión linear. En 873 pacientes, cada minuto que pasaba después del colapso la probabilidad de registrar FV disminuı́a (OR 0.92, 95% CI 0.89–0.95) y la de registrar ası́stole aumentaba (OR 1.13, 95%CI 1.09–1.18). El uso de BLS reducı́a estas tendencias en forma significativa para VF (OR 0.97, 95% CI 0.94–0.99) y para ası́stole (OR1.09 95% CI 1.05–1.13). Este efecto no se observó para otros ritmos. La amplitud de la VF disminuyó en el tiempo, significativamente menos para pacientes que recibieron BLS que para aquellos que no lo recibieron (p=0.009). La sobrevida disminuyó significativamente con la menor amplitud de la VF (OR 0.23 per mV, 95% CI 0.07–0.79) y con menos cruces de lı́nea de base (OR 0.80 por cruces de lı́nea de base por segundo, 95% CI 0.71–0.91). Nuestro estudio demuestra que el BLS y la VF como ritmo inicial, considerados como predictores ‘basales’ de sobrevida en modelos, mostraron no ser independientes entre ellos. La disminución en la amplitud de la VF y el aumento en la prevalencia de ası́stole son enlentecidas con el BLS. La predicción de sobrevida a partir solo de amplitud y cruces de lı́nea de base de la VF es limitada.
Palabras clave: RCP prehospitalaria; Fibrilación ventricular; Soporte vital básico