Defibrillation and the upper limit of vulnerability to fibrillation in a transthoracic Guinea pig model

Abstract

Recent studies have shown sustained tachyarrhythmias in guinea pigs. We hypothesized that guinea pigs could be used as a model of ventricular fibrillation, focusing on defibrillation waveform efficacy and the upper limit of vulnerability to fibrillation. In 10 male guinea pigs, an esophageal/apical pacing electrode configuration was used. The electrocardiogram (ECG) and arterial blood pressure were continuously monitored. T-wave and defibrillation shocks were applied transthoracically. A modified up-down protocol was used. After up-down testing was completed, a tachyarrhythmia was induced without electrical termination. All animals died of a sustained tachyarrhythmia. The monophasic DFT 50 (the 50% successful defibrillation voltage, 496 ± 176 V) was larger than the biphasic DFT 50 (364 ± 94 V, P < .005). The upper limit of vulnerability to fibrillation (ULV 50) (the 50% successful induction voltage) was correlated with the DFT 50 for both monophasic ( r = .82, P < .005) and biphasic shocks ( r = .88, P < .005). Its low cost and ease of handling may make the guinea pig a preferred model for some fibrillation and defibrillation studies.