Abstract 342: Developing an In Vivo Model of Ventricular Refibrillation
Ventricular refibrillation, defined as re-emergence of VF following successful defibrillation, is as frequent as 79% after out of hospital cardiac arrest, with at least 50% of patients experiencing more than 1 episode of refibrillation. Re-fibrillations are harder to defibrillate and are inversely associated with survival. The mechanism of refibrillation is not known. In order to test hypotheses on preventing or treating refibrillation, a reliable in-vivo refibrillation model is necessary. Pigs have been used as a reliable model to study the efficacy of CPR. Here we present a swine model of ventricular refibrillation following VF.
Methods & Results
Twenty-four Yorkshire pigs were anesthetized. Three Millar catheters were used to measure pressure from abdominal Aorta, RA and LV. An EP catheter was introduced in the RV to induce VF. VF was induced by burst pacing and left untreated for 4 minutes. Then chest compressions were delivered using a pneumatic device at a constant rate of 120/min and manual ventilation was delivered at 6 breaths/min. All animals were defibrillated after 3 min of CPR at 150J, and increasing energy in case of failure. After successful defibrillation, they were observed for a period of 30 min for any occurrence of refibrillation. Refibrillations were treated with defibrillation. The initial VF could not be defibrillated in 3 (12%). Refibrillation occurred in 13 (62%). The mean time to onset of refibrillation was 629 sec after successful defibrillation ranging from 8 to 1600 sec. Mean number of re-fibrillations was 1.14±1.15 (max: 4) with 33.33% (n=7) experiencing more than one episode of refibrillation. Forty-six percent of refibrillations occurred within first 5 min after defibrillation. Overall Survival was 37.5% (n=9). Survival was 38% in re-fibrillation group vs. 44.4% in non-refibrillation group (p=nsS). With regards to initiation, 60% of episodes were preceded by 1 PVC and 20% were preceded by 2 PVCs or more.
We have developed a swine model of ventricular re-fibrillation that resembles reported human data in terms of incidence of re-fibrillation and initiation following VF arrest. This model will serve as a test bed for different pharmacologic and interventional strategies focused on modulating refibrillation.
- © 2012 by American Heart Association, Inc.