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A Model of Ischemically Induced Ventricular Fibrillation for Comparison of Fixed‐dose and Escalating‐dose Defibrillation Strategies
Author(s) -
Niemann James T.,
Rosborough John P.,
Walker Robert G.
Publication year - 2004
Publication title -
academic emergency medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.221
H-Index - 124
eISSN - 1553-2712
pISSN - 1069-6563
DOI - 10.1197/j.aem.2003.12.018
Subject(s) - defibrillation , ventricular fibrillation , medicine , cardiology , fibrillation , population , shock (circulatory) , anesthesia , atrial fibrillation , environmental health
Objectives: Fixed‐ and escalating‐dose defibrillation protocols are both in clinical use. Clinical observations suggest that the probability of successful defibrillation is not constant across a population of patients with ventricular fibrillation (VF). Common animal models of electrically induced VF do not represent a clinical VF etiology or reproduce clinical heterogeneity in defibrillation probability. The authors hypothesized that a model of ischemically induced VF would exhibit heterogeneous defibrillation shock strength requirements and that an escalating‐dose strategy would more effectively achieve prompt defibrillation. Methods: Forty‐six swine were randomized to fixed, lower‐energy (150 J) transthoracic shocks (group 1) or escalating, higher‐energy (200 J–300 J–360 J) shocks (group 2). VF was induced by balloon occlusion of a coronary artery. After 1 or 5 minutes of VF, countershocks with a biphasic waveform were administered. The primary endpoint was successful defibrillation (termination of VF for 5 seconds) with ≤3 shocks. Results: VF was induced with occlusion or after reperfusion in 35 animals. Only five of 17 group 1 animals (29%, 95% CI = 10 to 56) could be defibrillated with ≤3 shocks; 15 of 18 group 2 animals (83%, 95% CI = 59 to 96) were defibrillated with ≤3 shocks (p < 0.002 vs. group 1). Nine of the group 1 animals (75%) that could not be defibrillated with 150‐J shocks were rescued with ≤3 shocks ranging from 200 to 360 J. Conclusions: In this ischemic VF animal model, defibrillation shock strength requirements varied among individuals, and when defibrillation was difficult, an escalating‐dose strategy was more effective for prompt defibrillation than fixed, lower‐energy shocks.