ORLANDO -- A person who suffers cardiac arrest outside the hospital is in imminent danger of dying, especially if defibrillation fails to rapidly shock the heart into resuming normal beating. A clinical trial performed by University of Washington researchers shows that administering an anti-arrhythmia medication, amiodarone, offers considerable promise in helping to resuscitate cardiac arrest victims.
Dr. Peter Kudenchuk, associate professor of medicine and director of arrhythmia services at University of Washington Medical Center, and colleagues performed the study, called ARREST (Amiodarone in the Out-of-Hospital Resuscitation of Refractory Sustained Ventricular Tachyarrhythmias).
They found that resuscitation to a stable heart rhythm was improved by 26 percent in people treated with intravenous amiodarone, compared to those who received all other standard treatments for cardiac arrest.
Among people in whom defibrillation shocks alone could only temporarily maintain a stable heart beat, amiodarone improved their chances of being admitted alive to the hospital by 56 percent.
Kudenchuk presented results of the unpublished study Nov. 12 at the American Heart Association's 70th Scientific Sessions in Orlando, Fla.
"Each year, more than a quarter of a million Americans suffer an unexpected cardiac arrest," said Kudenchuk. "The majority do not respond to defibrillation treatments alone, and more than two-thirds die before reaching the hospital."
Kudenchuk noted that the clinical trial is the first of its kind to compare the effectiveness of the anti-arrhythmia medication with all other standard treatments in patients who suffer out-of-hospital cardiac arrest and who are not responding to shock treatment.
The drug was administered to 504 people in Seattle and King County, Wash., who suffered cardiac arrest due to a dangerous heart rhythm (ventricular fibrillation) between November 1994 and February 1997. More than three-quarters of the victims were men, ranging in age from 20 to 94 years.
No other medication has been shown to have such effectiveness in treating shock-resistant cardiac arrest, said Kudenchuk.
He noted that the main treatment endpoint for the ARREST trial was being admitted alive to a hospital. The trial was not sufficiently large to evaluate the effect of treatment on the likelihood of being discharged from the hospital alive. "From a statistical standpoint, proving this would require far more patients and years of study," said Kudenchuk. Thus, although a slight improvement in survival to hospital discharge was observed in cardiac arrest victims treated with amiodarone, this was not felt to be conclusive by the investigators.
"ARREST has given us a new and powerful treatment for victims of shock-resistant cardiac arrest," said Kudenchuk. "But getting patients to the hospital alive is only the first hurdle. Further research is needed to find better ways of protecting the brain and heart from injury during cardiac arrest. That is what determines ultimate survival in those we are fortunate enough to resuscitate successfully."
Amiodarone is marketed as Cordarone I.V. by Wyeth-Ayerst Laboratories. The study was performed in conjunction with Medic One, Seattle's highly regarded emergency medical response service. The Medic One Foundation provided approximately two-thirds of the funding for the study and Wyeth-Ayerst, approximately one-third.
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Note to Reporters: Dr. Peter Kudenchuk can be reached at the AHA Scientific Sessions until Wednesday, Nov. 12, at the Orlando Marriott Hotel, 1-800-421-8001.