Antiarrhythmic drugs found beneficial when used by EMS treating cardiac arrest
April 4, 2016 - 12:53 PM
Researchers have confirmed that certain heart rhythm medications, when
given by paramedics to patients with out-of-hospital cardiac arrest who
had failed electrical shock treatment, improved likelihood of patients
surviving transport to the hospital. The study was published online in
the New England Journal of Medicine and helps answer a longstanding
scientific question about the effectiveness of two widely-used
antiarrhythmic drugs, amiodarone and lidocaine, for treating sudden
The study followed the patients from hospital admission to hospital
discharge. Although neither drug significantly improved the overall rate
of survival to hospital discharge, amiodarone showed a favorable trend
in that direction. Survival to discharge is the point at which a patient
is discharged from the hospital.
“This trial shows that amiodarone and lidocaine offer hope for
bringing patients back to life and into the hospital after cardiac
arrest,” said principal study author Peter Kudenchuk, M.D., a cardiac
electrophysiologist at the University of Washington Medical Center in
Seattle. “While the overall increase in survival to hospital discharge
of about 3 percent with amiodarone was not statistically significant, it
came very close. Importantly, there was a significant improvement in
survival to hospital discharge with either drug when the cardiac arrest
was bystander-witnessed.” A bystander-witnessed cardiac arrest is one
that is witnessed by another person.
Sudden cardiac arrest is a condition in which the heart suddenly or unexpectedly stops
beating, cutting off blood flow to the brain and other vital organs.
More than 300,000 people are treated for out-of-hospital cardiac arrest
each year, with the vast majority occurring at home, according to the
American Heart Association. Studies show that nationally only about
10 percent of people who suffer cardiac arrest outside the hospital
survive. Effective treatments, such as CPR and defibrillation, can
greatly increase a victim’s chance of survival. This study adds the
possibility of additional benefit from the use of the heart rhythm
EMS (emergency medical services) providers commonly use
antiarrhythmic drugs for out-of-hospital cardiac arrest that is not
responsive to defibrillation shocks to the heart for restoring its
normal rhythm. However, doctors remain unclear whether these drugs have
proven survival benefit or if any benefit might be undone by possible
drug side effects. As a result, use of these treatments by paramedics
The three-year study began in 2012, and randomized 3,026 patients
with out-of-hospital cardiac arrest caused by ventricular fibrillation
and ventricular tachycardia, life-threatening rhythms of the heart’s lower pumping chambers that are often resistant to electrical shock.
Researchers assigned the patients to treatment with amiodarone,
lidocaine, or neither drug (a saline placebo) by rapid injection, along
with all other standard resuscitation treatments. The study was
conducted by the Resuscitation Outcomes Consortium, which includes clinical sites in the United States and Canada.
“Survival among the approximately 1,900 patients in the study whose
cardiac arrest was witnessed by a bystander was improved significantly,
from about 23 percent to 28 percent, by either drug,” Dr. Kudenchuk
said. Better than half of study participants fit this
bystander-witnessed category, a group that was identified before the
study began as potentially more likely to respond to such treatment.
“This suggests treating patients as soon as possible after their
collapse might be a critical determinant of whether drugs like
amiodarone or lidocaine will have a significant clinical effect,” he
“I’m encouraged by the fact that though seemingly small, the 3-5
percent increase in survival reported in this trial means 1,800
additional lives could potentially be saved each year from cardiac
arrest,” Dr. Kudenchuk said. “We can and should strive to improve our
treatments for this all-to-common event. We believe this study is a
significant step in that direction.”
Adverse effects from the drugs were infrequent, and scientists are
continuing to analyze findings from the trial to gain additional insight
into its results.
Funding for this study was provided by NHLBI in partnership with the
U.S. Army Medical Research & Material Command, the Canadian
Institutes of Health Research, the Heart and Stroke Foundation of
Canada, and the American Heart Association. The study was presented at
the American College of Cardiology 2016 Scientific Sessions in Chicago.
EMS agencies and receiving hospitals that participated in this trial
are located in: Birmingham, Alabama; Vancouver, British Columbia;
Dallas-Fort Worth; Seattle-King County; Milwaukee; Ottawa-OPALS Group,
Ontario; Toronto; Portland, Oregon; San Diego; and Pittsburgh.
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