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Original Articles

Preshock Cardiopulmonary Resuscitation Worsens Outcome From Circulatory Phase Ventricular Fibrillation With Acute Coronary Artery Obstruction in Swine

Julia H. Indik, MD, PhD; Ronald W. Hilwig, DVM, MS, PhD; Mathias Zuercher, MD; Karl B. Kern, MD; Marc D. Berg, MD and Robert A. Berg, MD

From the Sarver Heart Center (J.H.I., R.W.H., M.Z., K.B.K., M.D.B., R.A.B.), the Department of Medicine (J.H.I., K.B.K.), and the Steele Research Center and Department of Pediatrics (M.D.B., R.A.B.), University of Arizona College of Medicine, Tucson, Ariz; the Department of Anesthesiology and Intensive Care (M.Z.), University Hospital, Basel, Switzerland; and the Department of Anesthesiology and Critical Care Medicine (R.A.B.), The Children’s Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pa.

Correspondence to Julia H. Indik, MD, PhD, Sarver Heart Center, University of Arizona College of Medicine, 1501 N Campbell Ave, Tucson, AZ 85724-5037. E-mail jindik{at}email.arizona.edu

Received September 28, 2008; accepted February 11, 2009.

Background— Some clinical studies have suggested that chest compressions before defibrillation improve survival in cardiac arrest because of prolonged ventricular fibrillation (VF; ie, within the circulatory phase). Animal data have also supported this conclusion, and we have previously demonstrated that preshock chest compressions increase the VF median frequency and improve the likelihood of a return of spontaneous circulation in normal swine. We hypothesized that chest compressions before 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 2 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 3 minutes of chest compressions before shock (n=13, preshock cardiopulmonary resuscitation group). In the preshock cardiopulmonary resuscitation group, median frequency was increased from 7.0±0.8 to 13.9±1.6 Hz after chest compressions (P=0.002). Despite the improved median frequency in the preshock cardiopulmonary resuscitation group, 24-hour survival with favorable neurological status was significantly worse in the preshock cardiopulmonary resuscitation 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 • myocardial infarction • heart arrest • ventricular fibrillation defibrillation

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CLINICAL PERSPECTIVE

Related Article

Preshock Cardiopulmonary Resuscitation Worsens Outcome From Circulatory Phase Ventricular Fibrillation With Acute Coronary Artery Obstruction in Swine

Julia H. Indik, Ronald W. Hilwig, Mathias Zuercher, Karl B. Kern, Marc D. Berg, and Robert A. Berg
Circ Arrhythm Electrophysiol 2009 2: 179-184. [Abstract] [Full Text] [PDF]