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The Shocking Story of Defibrillators: What They Do, Why They Do It

By Jo Ann LeQuang

Republish: EasyPublish™
Published: 30Jul2008
Word count: 1017
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Defibrillators are starting to become part of the common vocabulary. But do you actually know what one does and why you would need it?

The popular notion is that a defibrillator is required to help "re-start" a heart that has stopped. Technically, that is not true. Defibrillators deliver electricity to the heart to restore a faulty heart rhythm. The name for this situation is called "sudden cardiac arrest" or even "sudden cardiac death." You can see why that last name is falling out of favor, but it means the same thing. And, yes, many people (about 20%) who have "sudden cardiac death" survive it.

Sudden cardiac arrest typically occurs when the heart starts to beat dangerously fast. A rapid heart rate can be appropriate when the body is exercising or highly stressed. But sometimes the heart tries to beat at rates that are overly fast—200 or even 300 times a minute.

The healthy heart at rest beats about 60 times a minute or once a second. If you make a fist (which is about the size of your heart) and open and close it to simulate pumping action, you can see that the heart is pumping at a pretty good clip to maintain a normal rhythm.

Now imagine the heart trying to beat 120 times a minute—an appropriate rate for mild exercise. This means you would have to open and close your fist twice each second. The heart is still efficient at this rate, but it's hard work.

But let's double it—240 times a minute or four times a second. If your heart ever tried to beat 240 times a minute, it would no longer be able to pump efficiently. Try it with your fist and you see that you just can't keep up. Your movements have to become abbreviated. That's what happens during sudden cardiac arrest. Your heart is trying to beat so rapidly that it can no longer really pump. The heart muscle just quivers. Blood sloshes around in the heart instead of being pumped out.

In medical terms, your cardiac output drops to zero in a matter of seconds. This heart condition is usually attributable to a rhythm disorder called ventricular fibrillation (VF). But no matter what it is called, it is a sudden and potentially lethal heart rhythm.

Left untreated, a person with VF can die in as few as four minutes.

Sudden cardiac arrest from VF is not the same thing as a heart attack. A heart attack is essentially a "plumbing problem" of the heart, a situation where blockage in the "pipes" or blood vessels prevents blood flow. Other plumbing problems that can occur in the heart relate to the valves or the ability of the heart muscle to pump.

Cardiac rhythm disorders are electrical problems. They occur because of disorders in the heart's electrical system and they can happen in a person who has an otherwise "healthy heart."

The heart generates electricity to make it beat. That electricity flows through the heart along established conduction pathways. But sometimes an electrical impulse gets "stuck" on the pathway and makes endless loops, faster and faster, causing the heart to try to contract and relax to keep up with the electrical signals.

A defibrillator works by sending a powerful jolt of electricity to the heart. The heart's electrical system responds to electricity.

VF occurs when an electrical accident causes the heart to try to beat too rapidly. A sudden influx of a large amount of electricity literally captures the attention of every single heart cell and gets them all "reset" or back on the same page.

After a defibrillation pulse (which can be a very large amount of energy delivered in a fraction of a second in order to be sure to get the attention of every single cell in the heart), there is usually a pause of a second or even a few seconds.

Then the heart resumes generating electricity and conducting it normally.

External defibrillation relies on special equipment and two large paddles that send the electricity through the chest. This is the defibrillation you see in the movies when the doctor yells, "Clear!" and then a jolt of energy travels from a generator through one paddle to the other.

Defibrillation equipment is standard in hospitals, many clinics, and it is increasingly common in airports, schools, and other public places. The reason for this is obvious: sudden cardiac arrest comes on suddenly, without warning, and there is often not enough time to get the victim to a hospital.

That was why a physician named Michel Mirowski invented an implantable defibrillator.

Dr. Mirowski's best friend died of sudden cardiac arrest because he could not get rescue defibrillation in time to save his life. Dr. Mirowski theorized that if a defibrillator could be implanted in the body, people could survive sudden cardiac arrest even if it happened when they were far from a hospital or an external defibrillator.

That was back in the 1980s and, believe it or not, Dr. Mirowski found many physicians who insisted what he wanted to do was technologically impossible and medically unethical. It was neither. Mirowski lived to see implantable defibrillators designed, developed, and commercially available by 1988.

Today, implantable defibrillators are common. Most of them contain "built-in" pacemakers so that the pacemaker-defibrillator device is a standard of care.

The pacemaker paces a heart that beats too slowly or too erratically. The defibrillator shocks a runaway rhythm back to normal.

Defibrillators are in widespread use all over the world. Studies have proven that they not only help save lives, they actually work better than most drug therapy for people prone to electrical problems of the heart. This does not mean that defibrillator patients do not have to take drugs; many physicians recommend what doctors called "adjunctive therapy," which is a fancy way of saying "belts and suspenders." In other words,a person woulkd get a defibrillator (to rescue him from dangerous rhythm disorders) but also take heart medications (to help prevent those rhythm disorders from occurring).

Is there a pacemaker or defibrillator in your future? Learn more about them at http://www.pacemaker411.com . Pacemakers and defibrillators are safe, effective, and in widespread use ... but there is a lot of misinformation about how they work and what they do. They have proven life-saving and life-enhancing benefits. To learn more, visit http://www.pacemaker411.com .

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