Shocking the heart after prolonged cardiac arrest may be harmful, say Pitt researchers

October 08, 2002

SEATTLE, Oct. 8 - Delaying by 10 minutes before defibrillating a patient's heart in cardiac arrest - the typical amount of time it takes most emergency medical professionals to respond to a call - probably won't help and may even be detrimental, suggests a study performed by researchers in the department of emergency medicine at the University of Pittsburgh School of Medicine.

Results of their study were reported today at the American College of Emergency Physicians Scientific Assembly 2002, Research Forum at the Washington State Convention and Trade Center in Seattle. "Although rapid defibrillation is hands down the best method to resuscitate victims minutes after sudden cardiac arrest, we now have additional evidence that indicates the longer someone is in prolonged cardiac arrest, providing immediate defibrillation is not the most effective way to resuscitate because the injured heart is only further damaged by shocking it. This evidence suggests we should try other treatment options before defibrillation," stated James Menegazzi, Ph.D., research professor of emergency medicine at the University of Pittsburgh School of Medicine and lead author of the study.

Approximately 10 minutes after the onset of cardiac arrest, when the heart abruptly stops beating, little or no energy remains in the heart and it loses its ability to pump blood.

In animal studies, the researchers copied two clinical scenarios for sudden cardiac arrest in real time by waiting between eight to 10 minutes and 10 to 12 minutes from the onset of cardiac arrest to begin resuscitation efforts. This is typically the same time frame it takes for first responders to arrive at the scene of a patient in cardiac arrest. After desired level of cardiac arrest was reached, the subjects were treated with one of three strategies: immediate defibrillation; a combination therapy of cardiopulmonary resuscitation (CPR) first, intravenous drugs second and defibrillation last; or intravenous drugs and CPR administered simultaneously before defibrillation.

Out of the three resuscitation strategies, the researchers found that immediate defibrillation was least effective and there was also a significant delay in getting restored circulation. There were no significant differences in the subjects that were resuscitated at eight to 10 minutes or at 10 to 12 minutes.
In addition to Dr. Menegazzi, co-authors of the study were Clifton Callaway, M.D., assistant professor of emergency medicine; Henry Wang, M.D., visiting instructor of emergency medicine; David Hostler, Ph.D., visiting research instructor of the department of emergency medicine; Kristofer Fertig, B.S., research specialist in emergency medicine; and Lawrence Sherman, M.D., clinical assistant professor of emergency medicine.

This study was funded in part by the Pittsburgh Emergency Medicine Foundation.

Note to journalists attending the ACEP Research Forum: "Immediate Countershock after Prolonged Ventricular Fibrillation," (Poster presentation #8) is being presented in Room 618 at 8:30 a.m. PT, Tuesday, Oct. 8.


Maureen McGaffin
Lisa Rossi
PHONE: (412) 647-3555
FAX: (412) 624-3184

University of Pittsburgh Medical Center

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