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Why Are They
Important?
Sudden
cardiac arrest accounts for at least 350,000 deaths each year in the
United States and some authorities believe the number is much higher.
Whatever the accurate number, cardiac arrest kills more people than all
forms of cancer combined.
Cardiac
arrest results from a defect in the electrical impulses that control the
heart’s rhythm. It is not a synonym for heart attacks that are usually
caused by blockage of the veins and arteries leading to and from the
heart. The analogy is that cardiac arrest is an electrical defect whereas
heart attacks result from problems with the plumbing. People who suffer
heart attacks often remain conscious during and after the attack and they
are able to breathe on their own. Cardiac arrest victims lose
consciousness, stop breathing and their hearts beat erratically. If
intervention isn’t rapid, they usually die.
For the
past twenty years, CPR has been the treatment of choice for cardiac
arrest. Oxygen is provided to an unconscious person and chest compressions
pump blood around his body. While better than no treatment, cardiac arrest
victims treated by CPR alone survive only two to five percent of the time.
CPR buys time until more effective treatments can be administered.
AEDs
provide rescuers with these more effective treatments. The most common
rhythm problem leading to cardiac arrest is ventricular fibrillation. This
quivering of the heart muscle (likened to shaking a bowl of Jell-O)
causes the heart to stop circulating blood to the brain. Breathing stops
and shortly thereafter the heart stops as well. Unfortunately, CPR does
nothing to restore normal heart rhythm and the longer CPR is performed,
the less the chance of survival.
The same
CPR rescuer, equipped with an AED, has a chance to improve the odds of
survival significantly. If the AED senses ventricular fibrillation, it
authorizes a shock to be given. The shock causes the heart to stop for a
millisecond after which the victim’s own electrical system may cause it to
start beating normally. Not all rescues involving an AED are successful,
but where they are deployed widely and used quickly, survival rates of 50%
or higher have been reported – a far cry from the 2-5% survival rates of
CPR alone.
Defibrillation is most effective when used as soon after an arrest as
possible. The chance of success decreases by seven to ten percent for
every minute of delay.
Rescuers
must remember that if nothing is done for a cardiac arrest victim, he is
probably going to die. Even with prompt CPR he is probably going to die
before the ambulance arrives. Defibrillation applied shortly after his
collapse gives him a fair chance of survival. What better reason could
there be for implementing AED programs?
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