Ventricular Defibrillation With Triphasic Waveforms

Abstract

Background —It has been reported that triphasic defibrillation waveforms cause less myocardial injury than biphasic waveforms. This study compared the defibrillation thresholds (DFTs) of triphasic and biphasic waveforms. Methods and Results —DFTs were determined for a transvenous lead system and a 300-μF-capacitor defibrillator. In 8 pigs (group 1), DFTs were determined for 5 triphasic waveforms with tilts of 80%, 83%, and 86% and for 1 biphasic waveform. DFTs were determined in another 8 pigs (group 2) for 2 triphasic and 4 biphasic waveforms with tilts of 43%, 49%, and 56%. In both groups, a biphasic waveform from a 140-μF-capacitor defibrillator was also evaluated, and both shock polarities were tested for each waveform. In group 1, with the 300-μF-capacitor defibrillator, the leading-edge voltage and energy stored at DFT were significantly lower for triphasic waveforms with phase-duration ratios of 50/33/17 and an anode at the right ventricular electrode for phase 1 than for biphasic waveforms ( P <0.001). In group 2, the stored energy of triphasic waveforms with 56% and 49% tilt was significantly lower than that of biphasic waveforms with the same tilts for anodal but not cathodal phase 1 at the right ventricular electrode. Electrode polarity significantly affected the DFT of triphasic waveforms for both studies. Conclusions —Some 80% tilt triphasic waveforms defibrillate more efficiently than biphasic waveforms with a 300-μF-capacitor defibrillator. The triphasic waveforms for both groups were not superior to 140-μF-capacitor biphasic waveforms. The efficacy of triphasic waveforms depends on phase durations and electrode polarity.

Simultaneous Comparison of Many Triphasic Defibrillation Waveforms

“…Quadriphasics show superior performance but only when the patient’s impedance is elevated [13]. Polarity may also affect the relative efficacy of triphasic waveforms [14]. Thus, triphasics may indeed be superior in some models or under certain conditions but based on our findings and the body of evidence, we conclude that triphasic waveforms cannot be considered uniformly superior to biphasic waveforms.…”

Ensaio pré-clínico com desfibrilador externo

“…Com base em consultoria estatística, os animais foram subdivididos em quatro grupos segundo: Grupo I: quatro animais, empregado o protótipo de equipamento a 50 J (PO-DEA 50 J); Grupo II: quatro animais, empregado o protótipo de equipamento a 100 J (PO-DEA 100 J); Grupo III: quatro animais, empregado o equipamento referência a 50 J (R-DEA 50J); e Grupo IV: quatro animais, empregado o equipamento referência a 100 J (R-DEA 100 J) (Quadro 1). A avaliação estatística para definição do número de animais para o estudo foi baseada em estudos publicados que envolvem o sistema cardiovascular, como o experimento de Walker et al, 14 que avaliou a eficácia de seis formas de onda em episódio de fibrilação ventricular comparando choques monofásicos de 200 J e bifásicos de 150 J em grupos de seis e oito suínos, o de Li et al, 16 onde foi estudada a eficácia das formas de ondas bifásicas pulsada e retilínea utilizando seis porcos domésticos, e o de Huang et al, 20 que comparou os limiares de desfibrilação das formas de onda trifásica e bifásica em grupos de oito porcos. A ordem dos animais para a realização dos experimentos foi randomizada para os grupos e de forma cega para os laboratórios de análise.…”

Automatic Implantable Cardioverter-defibrillators

“…All of these factors have been implicated as determinants of defibrillation efficacy. Although triphasic waveforms have been shown to be superior to biphasic ones in some circumstances (40,42), other studies have shown no difference or even a trend to superiority of the biphasic shape (13,25,44,57). After clinical trials (9), the biphasic waveform has become the clinical standard for implantable devices.…”