TREATMENT OF INTRACTABLE VENTRICULAR-FIBRILLATION WITH PROMPT CIRCULATORY SUPPORT USING A BIVENTRICULAR ASSIST DEVICE IN PIGS - AN EXPERIMENTAL-STUDY

Refractory ventricular fibrillation (VF), intractable to conventional therapy, can be converted into a stable cardiac rhythm by immediate ventricular volume unloading using a form of mechanical circulatory assist (MCA). We investigated the efficacy of MCA in a controlled animal study in which 20 pigs were subjected to intermittent occlusions (5 times) of the left descending coronary artery (5 min. occlusion +10 min. reperfusion). 12 of the 20 animals (60 %) developed 14 events of VF. 64 % of VF developed during reperfusion (p < 0.05). Countershock was attempted up to eight times and was successful in 5 of the 14 events (36%) (primary defibrillation, PD). When conversion was not achieved, total biventricular bypass was instituted. Mean perfusion time between countershock attempts was 24.4 +/- 15.3 min. All animals (n = 9) with cardiac assistance were successfully defibrillated (secondary defibrillation, SD), (p < 0.05). Hemodynamic parameters after SD were not significantly different from those after PD (p > 0.05). Survival rate following PD was 66.6%. Six animals were ultimately weaned from cardiac assistance following SD. Three others died of progressive cardiogenic shock in the six hour follow-up period following SD. These non-survivors had a significantly longer VF time than the survivors (41.7 +/- 10.4 vs. 15.8 +/- 8.0, p < 0.05). Overall survival after SD was the same as that for PD: 66.6% (p > 0.05). These results show that prompt conversion of VF into a stable cardiac rhythm is a prerequisite to recovery. Our data did not reveal to what extent reduction of myocardial distention or restoration of coronary perfusion contributed to successful defibrillation during cardiac assistance. In this study MCA proved an effective adjuvant to conventional therapy for the treatment of intractable VF.