on February 18, 2009
Published online before print February 18, 2009, doi: 10.1161/CIRCEP.108.824862
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Original Article |
Pre-shock CPR Worsens Outcome from Circulatory Phase VF with Acute Coronary Artery Obstruction in Swine
1 University of Arizona;
2 University of Arizona and University Hospital, Basel;
3 University of Arizona and Children's Hospital of Philadelphia
4 E-mail: jindik{at}email.arizona.edu
Background—Some clinical studies have suggested that chest compressions prior to defibrillation improve survival in cardiac arrest due to prolonged ventricular fibrillation (VF)(i.e., within the Circulatory Phase). Animal data have also supported this conclusion, and we have previously demonstrated that pre-shock chest compressions increase the VF median frequency and improve the likelihood of a return of spontaneous circulation (ROSC) in normal swine. We hypothesized that chest compressions prior to defibrillation in a swine model of acute myocardial ischemia would also increase VF median frequency and improve resuscitation outcome.
Methods and Results—Twenty six swine were subjected to balloon occlusion of the left anterior descending coronary artery for two hours. The balloon was removed and VF was induced and untreated for 8 minutes. Swine were then treated with up to 3 stacked defibrillation shocks (N=13, shock first group) or three minutes of chest compressions prior to shock (N=13, pre-shock CPR group). In the pre-shock CPR group, median frequency was increased from 7.0±0.8 Hz to 13.9±1.6 Hz after chest compressions, P=0.002. Despite the improved median frequency in the pre-shock CPR group, 24-hour survival with favorable neurological status was significantly worse in the pre-shock CPR group (1/13) compared with the shock first group (8/13, P=0.01).
Conclusions—In a swine model of prolonged VF in acute myocardial ischemia, 24-hour survival with favorable neurological status was more likely when defibrillation was performed first without preceding chest compressions. Myocardial substrate is an important factor in determining the optimal resuscitation strategy.
Key Words: cardiopulmonary resuscitation • defibrillation • heart arrest • myocardial infarction • ventricular fibrillation
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