Predicting the success of defibrillation by electrocardiographic analysis
Introduction
Current recommendations call for immediate and repetitive electrical defibrillation in settings of ventricular fibrillation (VF) during cardiac resuscitation [1]. However, there is increasing evidence that repetitive high-energy electrical shocks produce myocardial damage and compromise post resuscitation myocardial function and survival [2], [3], [4]. We were therefore prompted to identify a clinically applicable method for timing the delivery of an electrical shock when the shock is likely to restore spontaneous circulation.
Earlier investigations suggested that electrical properties of VF wavelets reflect, at least in part, the capability of the myocardium to convert to a regular rhythm and utilized the amplitude of VF wavelets to predict the success of a defibrillation attempt [5], [6]. More sophisticated analyses of median frequency [7], [8], [9] and dominant frequency [10], [11] have also been predictive of the success of electrical defibrillation.
Electrocardiographic (ECG) waveforms are routinely recorded and interpreted from multiple leads by professional rescuers. With automated external defibrillators (AEDs), precordial electrodes are utilized together with computer based intelligence for detection of a shockable rhythm and specifically ventricular tachycardia or VF. AEDs prompt the rescuer to discontinue precordial compression during ‘hands off’ intervals for ECG rhythm analysis and during charging of the capacitor. However, interruptions of precordial compression are followed by reductions of coronary perfusion pressure (CPP). Reductions in CPP below threshold values compromise the success of electrical shocks, especially after prolonged cardiac arrest [12]. In the routine operation of AEDs, precordial compression may be repetitively interrupted for as long as 20 s with corresponding decreases in the success of electrical defibrillation and restoration of spontaneous circulation.
In the present study, we prospectively tested a previously described ECG analysis technique [13], [14] and its capability to provide a real-time indicator for prediction of the success of defibrillation with return of spontaneous circulation (ROSC) during uninterrupted precordial compression and ventilation.
Section snippets
Materials and methods
Experiments were performed on ten male domestic pigs. All animals received humane care in compliance with the Guide for the Care and Use of Laboratory Animals, formulated by National Research Council and published by National Academy Press in 1996. The protocols were approved by the Institutional Animal Care and Use Committee of the Institute of Critical Care Medicine.
Results
A total of 34 electrical defibrillation attempts were made on 10 animals. Outcomes are shown in Table 1 and data on individual animals in Table 2. The mean AMSA value was 25±4 mV Hz for animals in which spontaneous circulation was restored and 14±5 mV Hz when the defibrillation attempt was unsuccessful (P<0.001). An AMSA value of 21 mV Hz or greater predicted restoration of a perfusing rhythm in 7 of 8 instances and AMSA of 20 mV Hz or less correctly predicted failure of electrical resuscitation in
Discussion
In our experimental porcine model of cardiac arrest due to VF, AMSA value was displayed continuously and updated at 5 s intervals. AMSA served as a real-time predictor of whether an electrical shock would restore a perfusing rhythm. AMSA was not invalidated by artifacts resulting from precordial compression.
Our findings extend an earlier report from our group. The AMSA threshold value of 21 mV Hz had been previously identified [14]. The earlier study was retrospective and demonstrated that the
Acknowledgements
This research was supported by NIH Small Business Research Innovation Grant No. R43HL62075-01 in collaboration with the Survivalink Corporation, Minneapolis, MN.
Fundamento: Investigámos uma técnica de análise do sinal electrocardiográfico para prever se um choque eléctrico reverteria uma fibrilhação ventricular (FV) no sentido de minimizar os efeitos lesivos de choques repetidos durante a Reanimação Cardiopulmonar (RCP). Métodos e resultados: Utilizou-se um modelo estabelecido de RCP. Induziu-se fibrilhação ventricular em porcos domésticos de 40Kg anestesiados. A desfibrilhação foi tentada após 4 ou 7 minutos de FV não tratada. Quando a desfibrilhação
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Fundamento: Investigámos uma técnica de análise do sinal electrocardiográfico para prever se um choque eléctrico reverteria uma fibrilhação ventricular (FV) no sentido de minimizar os efeitos lesivos de choques repetidos durante a Reanimação Cardiopulmonar (RCP). Métodos e resultados: Utilizou-se um modelo estabelecido de RCP. Induziu-se fibrilhação ventricular em porcos domésticos de 40Kg anestesiados. A desfibrilhação foi tentada após 4 ou 7 minutos de FV não tratada. Quando a desfibrilhação falhou, fez-se 1 minuto de compressão cardı́aca externa e ventilação mecânica antes de qualquer outra tentativa de desfibrilhação. Computorizou-se o espectro de amplitude de frequências de ondas de FV digitalmente filtradas com análise Fourier durante a compressão cardı́aca externa não interrompida, a partir de eléctrodos colocados de forma convencional, um infraclavicular à direita e outro apical esquerdo. De um total de 34 tentativas de desfibrilhação eléctrica, foi possı́vel Recuperar Circulação Espontânea (RCE) em 24 animais. A Amplitude de Análise Espectral (AMSA) de 21 mV Hz tem um valor predictivo negativo de 0.96 e um valor predictivo positivo de 0.78. Conclusões: A AMSA foi capaz de prever com um valor predictivo altamente negativo quando um choque eléctrico falha em restaurar a circulação espontânea durante a RCP. Este método preenche potencialmente a necessidade de minimizar tentativas de desfibrilhação ineficazes e os efeitos adversos que estas têm no miocárdio.
Palavras chave: Amplitude de Análise Espectral; Fibrilhação ventricular; Desfibrilhação; RCP; Paragem cardı́aca; Rlectrocardiografia
Antecedentes: En un esfuerzo por minimizar los efectos nocivos de las descargas desfibrilatorias repetidos durante RCP, investigamos una técnica de análisis de los signos electrocardiográficos para predecir si la fibrilación ventricular (VF) serı́a revertida por una descarga eléctrica. Métodos y resultados: Se utilizó un modelo establecido de RCP. Se indujo eléctricamente una VF en cerdos domésticos de 40 kgs., anestesiados después de 4 ó 7 minutos de VF no tratada. se intentó la desfibrilación. Si no se revertı́a la VF, se realizó un minuto de compresión torácica y ventilación, precediendo cada intento subsecuente de desfibrilación. El espectro de amplitud de frecuencia de las ondas la VF, de electrodos convencionales, infraclavicular derecho y apical izquierdo, durante compresiones torácicas ininterrumpidas, filtrado digitalmente, fue computado con el análisis de Fourier. De un total de 34 intentos de desfibrilación eléctrica, 24 animales retornaron a circulación espontánea (ROSC). El valor de 21mV Hz en un análisis de espectro de amplitud (AMSA) tuvo un valor predictivo negativo de 0.96 y un valor predictivo positivo de 0.78. Conclusiones: El AMSA predijo cuando la descarga eléctrica falları́a en provocar retorno a circulación espontánea durante la RCP con un alto valor predictivo negativo. Este método satisface potencialmente la necesidad de minimizar los intentos de desfibrilación inefectiva y sus efectos deletéreos correspondientes en el miocardio.
Palabras clave: Análisis de espectro de amplitud; Fibrilación ventricular; Desfibrilación; RCP; Paro cardı́aco; Electrocardiografı́a