|Automated External Defibrillators and CPR Are
Equally Helpful for Sudden Cardiac Arrest in the Home
Study Finds AEDs Underused at Home
The first study to explore the use of automated external defibrillator
(AEDs) in the home has found that although the safe and easy-to-use
devices are effective for certain types of cardiac arrest, they
were underused. The Home Automated External Defibrillator Trial
(HAT), a randomized international clinical trial, was supported
by the National Heart, Lung, and Blood Institute (NHLBI) of the
National Institutes of Health.
Researchers will present their findings from the international
study at the 2008 American College of Cardiology (ACC) Scientific
Sessions in Chicago April 1. The results are being published online
simultaneously by the New England Journal of Medicine and will
appear in the April 24 print edition. An editorial by David Callans,
M.D., of the University of Pennsylvania accompanies the article
Researchers followed 7,001 heart attack patients at moderate risk
of sudden cardiac arrest who had a spouse or other live-in companion
who agreed to take conventional steps to respond to a sudden cardiac
arrest — calling emergency medical services (EMS) and performing
cardiopulmonary resuscitation (CPR) — with households that
were asked to use an AED before taking conventional life-saving
steps. After an average of just over three years of follow-up,
researchers found that survival rates were about the same between
those who had an AED in the home and those who did not. However,
there were relatively few sudden cardiac arrests, and only 39 percent
of these events were witnessed at home. The study was conducted
in 178 clinical sites in the United States, Canada, Britain, New
Zealand, Australia, Germany, and the Netherlands.
"Cardiac arrest is a top killer of Americans, and this study shows
that the strategies of placing an AED in the home and of being
prepared to give CPR are equally effective at saving lives in a
population at risk for sudden cardiac arrest," noted Elizabeth
G. Nabel, M.D., NHLBI director. "The important message here is
that every minute counts, and quick action is key. Use an AED if
one is handy or perform CPR — and always call for help by
emergency medical professionals, such as by dialing 911."
Every two to three minutes, someone in the United States goes
into cardiac arrest, and at least 95 percent of cases end in death
within a few minutes. Three out of four sudden cardiac arrests
take place when the patient is at home. During sudden cardiac arrest,
the heart suddenly and unexpectedly stops beating effectively;
blood stops flowing to the brain and other vital organs, and the
individual collapses into unconsciousness and stops breathing.
Although sudden cardiac arrest is not the same as a heart attack,
which is the result of a loss of blood supply to the heart muscle,
a heart attack increases the risk for sudden cardiac arrest.
The most common cause of sudden cardiac arrest is ventricular
fibrillation, in which a problem in the heart's internal electrical
system causes the large pumping sections of the lower part of the
heart (the ventricles) to disrupt the normal rhythm. In these cases,
an electric shock from an AED within a few minutes of onset can
significantly improve a patient's chance of survival by restoring
the heart to its normal rhythm. CPR has also been shown to be effective
in increasing survival from sudden cardiac arrest.
"The long-term survival rates of all of the HAT participants who
went into cardiac arrest were significantly higher than what is
typically found in the general population, and fewer of the participants
than expected had sudden cardiac arrest," noted Gust H. Bardy,
M.D., of the Seattle Institute for Cardiac Research, lead author
of the study. "We believe that this is because of the optimal medical
therapy and coronary revascularization that all HAT participants
received following heart attack. Moreover, although the control
arm mortality rates in HAT were equal to the AED group, it is not
routine practice to train spouses or other companions following
a patientís heart attack on why and how to call emergency medical
services for help and how to perform CPR. I believe this should
be routine practice following a patientís heart attack, regardless
of whether they have an AED in the home."
AEDs detect the patient's heart rhythm through electrodes that
are applied to a patient's chest. If the AED determines that the
problem is caused by ventricular fibrillation, the AED instructs
the user to hit a button to deliver an electric shock. The AED
transmits the shock through the electrodes, then rereads the heart
rhythm to determine if another shock is needed. The machine does
not recommend or administer a shock if the cause of the abnormal
rhythm cannot be treated by the shock. HAT researchers found no
evidence of inappropriate uses of the AED by lay users.
All HAT participants previously had a heart attack and were at
moderately increased risk for sudden cardiac arrest. Participants
also had to have a family member or other live-in companion who
was willing to follow specific steps to immediately help the participant
in cardiac arrest; these steps were described in a training video
and through discussions with study personnel. One-half of the companions
(control group) was asked to call EMS and perform CPR immediately;
the other half of the group was asked to use an AED before calling
EMS (or at the same time, if there were two bystanders) and performing
CPR. Participants were followed for about 3 years (ranging from
20 months to 56 months).
Overall, 450 participants died during the study, with nearly equal
numbers of participants in the control group (228 or 6.5 percent)
and the AED treatment group (222 or 6.4 percent). Participants
were equally likely to die from sudden cardiac arrest (35.6 percent)
as from other causes not related to cardiovascular disease (37.8
percent), and 160 deaths during the study were due to sudden cardiac
Of the 117 sudden cardiac arrests that occurred at home, only
one-half (58) of them were witnessed by another member of the household.
"We knew that the vast majority of sudden cardiac arrests would
happen at home, but we didn't expect that so few would be witnessed
by a spouse or other member of the household," explained Bardy. "This
of course dramatically limits the chance that someone would be
there to use an AED or to perform CPR. However, when the AEDs were
used, they were safe and effective."
AEDs were used by at-home bystanders on 32 HAT participants, with
ventricular fibrillation detected in 15 participants. Fourteen
of these participants were shocked, and ventricular fibrillation
was terminated in each case. There were no device failures. Overall,
among the participants in the AED group who used the AED for ventricular
fibrillation in the home, four of the 14 participants defibrillated
(28.6 percent) survived long term — an improvement over the estimated
2 to 6 percent long-term survival rates typically reported. In
addition, AEDs were used on seven neighbors or visiting friends,
and shock was advised and successfully given in four individuals,
of whom two survived long-term.
The AEDs used in the study are the same types of devices that
are now available in many airports, fitness centers, and other
public places, which have been shown to be safely and easily used
by bystanders with little training to perform life-saving treatment
on individuals in cardiac arrest.
"Studies of public access to AEDs have shown that AEDs can be
highly effective in helping people survive sudden cardiac arrest," said
Eleanor B. Schron, PhD, NHLBI project officer of the study and
a coauthor of the paper. For example, in the NHLBI-supported Public
Access Defibrillation Trial, nearly twice as many people survived
sudden cardiac arrest in communities where volunteers were trained
to use AEDs as well as CPR compared to communities where community
volunteers learned CPR only.
"Today's findings are consistent with other studies that show
that bystanders with little training can safely and effectively
use AEDs," she noted. "HAT gives us new insight into how AEDs are
used in the home, and, unfortunately, we found that AEDs were underused
in the home."
Philips Medical Systems and Laerdal Medical donated HeartStart
Home Defibrillators for use by participants in the AED group. The
HeartStart is the only FDA-approved home defibrillator available
without a prescription.
To interview Dr. Schron, call the NHLBI Communications Office
at (301) 496-4236. To speak with Dr. Bardy, please contact the
Seattle Institute for Cardiac Research at (206) 529-1117.
For more information:
Part of the National Institutes of Health, the National Heart,
Lung, and Blood Institute (NHLBI) plans, conducts, and supports
research related to the causes, prevention, diagnosis, and treatment
of heart, blood vessel, lung, and blood diseases; and sleep disorders.
The Institute also administers national health education campaigns
on women and heart disease, healthy weight for children, and other
topics. NHLBI press releases and other materials are available
online at: www.nhlbi.nih.gov.
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and supporting basic, clinical and translational medical research,
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