Electrical induction of ventricular fibrillation for resuscitation from postcountershock pulseless and asystolic cardiac arrests

Background-There is increasing evidence that defibrillation from prolonged ventricular fibrillation (VF) before CPR decreases survival. It remains unc lear, however, whether harmful effects are due primarily to initial counter shock of ischemic myocardium or to resultant postdefibrillation rhythms (ie , pulseless electrical activity [PEA] or asystole). Methods and Results-We induced 15 dogs into 12 minutes of VF and randomized them to 3 groups. Group I was defibrillated at 12 minutes and then adminis tered advanced cardiac life support (ACLS); group 2 was allowed to remain i n VF and was subsequently defibrillated after 4 minutes of ACLS; group 3 wa s defibrillated at 12 minutes, electrically refibrillated, and then defibri llated after 4 minutes of ACLS. All group I and 3 animals were defibrillate d into PEA/asystole at 12 minutes. After 4 minutes of ACLS, group 2 and 3 a nimals were effectively defibrillated into sinus rhythm. The extension of V F in group 2 and 3 subjects paradoxically resulted in shorter mean resuscit ation times (251 +/- 15 and 245 +/-7 seconds, respectively, versus 459 +/- 66 seconds for group 1; P <0.05) and improved 1-hour survival (10 of 10 gro up 2 and 3 dogs versus 1 of 5 group 1 dogs; Fisher's exact, P <0.005) compa red with more conservatively managed group I subjects. Conclusions-Precountershock CPR during VF appears more conducive to resusci tation than CPR during postcountershock PEA or asystole. The intentional in duction of VF may prove useful in the management of PEA and asystolic arres ts.