Open‐Chest Epicardial “Surgical” Defibrillation:

Abstract

The aim of the study was to compare biphasic versus monophasic shocks for open-chest epicardial defibrillation. Transthoracic biphasic waveform shocks require less energy to terminate ventricular fibrillation compared to monophasic waveform shocks. However, if biphasic shocks are effective for open-chest epicardial ("surgical") defibrillation has not been established. Twenty-eight anesthetized adult swine (15-25 kg) underwent a midline sternotomy. Ventricular fibrillation was electrically induced. After 15 seconds of ventricular fibrillation, each pig in group 1 (n = 16) randomly received damped sinusoidal monophasic epicardial shocks and truncated exponential biphasic epicardial shocks from large (44.2 cm2) paddle electrodes at eight energy levels (2-50 J). Pigs in group 2 (n = 12) received monophasic and truncated exponential biphasic shocks from small (15.9 cm2) paddle electrodes. In group 1 (large paddle electrodes), the overall percent shock success rose from 15 +/- 9% at 2 J to 97 +/- 3% at 50 J. In this group there was no significant difference in percent of shock success between damped sinusoidal monophasic and biphasic waveform shocks. In group 2 (small paddle electrodes), biphasic shocks yielded a significantly higher percent of shock success than monophasic shocks at mid-energy levels from 7 to 20 J (all P < 0.01). With small surgical paddle electrodes, biphasic waveform shocks demonstrated a significantly higher percent of shock success rate compared to monophasic waveform shocks. With large paddle electrodes, the two waveforms were equally effective.

Combining stimulus direction and waveform for optimization of threshold stimulation of isolated ventricular myocytes

“…Biphasic stimulating waveforms have been shown to be more effective and safer than monophasic waves during defibrillation-like electric stimulation (Jones and Jones 1984, Osswald et al 1994, Zhang et al 2003. Biphasic waves are also more effective to revert prolonged ventricular fibrillation (Walcott et al 1998), when myocardial electrophysiological deterioration is evident (Tovar and Jones 2000).…”

Letalidade de miócitos cardíacos de rato submetidos a estímulos multidirecionais

“…Faddy et al (2003) observaram que choques desĄbrilatórios com forma de onda bipolar permitem uma diminuição de 35 % na amplitude do estímulo para uma mesma eĄciência desĄbrilatória e que choques bipolares reduzem o risco de persistência da FV em 81 % quando comparados com choques monopolares de mesma intensidade. Zhang et al (2003), por sua vez, identiĄcaram uma maior taxa de desĄbrilação bem sucedida para estímulos bipolares ao aplicar choques com diversos níveis de energia em suínos.…”