Open-thorax guinea pig model for defibrillation

Background and Purpose: Guinea pigs are used as models for study of ventric ular tachyarrhythmias (VT); however, the tachyarrhythmia often is transient and does not persist. We developed an open-thorax guinea pig model of sust ained ventricular fibrillation (VF), Method Bilateral thoracotomy was performed on eight guinea pigs weighing 86 5 to 1,464 g, and two sutures were positioned in the right ventricular apex for the purpose of pacing. Two methods were used to induce VF: a 50-Hz bur st (normal pacing), and an initial 15 beats at 70% of the R-R interval foll owed by a 100-Hz burst for 84 beats (rapid pacing). Fifteen attempts at ind ucing VF were performed by use of each method. Blood pressure was recorded before and after development of VF, which was defined as VT with mean blood pressure consistently <10 mm Hg. A final observation was obtained using th e normal pacing method without defibrillation, Results: Use of both methods successfully induced VF, A significant relatio nship between body weight >1,021 g and ability to sustain and survive VF wa s detected. Conclusion: The guinea pig is a useful rodent model for the study of VF and defibrillation.