If you've ever watched medical shows on television, you've probably seen people on the brink of death shocked back to life by a doctor who yells "clear" and delivers several jolts of electricity to the chest.

Now you can perform this type of procedure in your own home with an automated external defibrillator (AED).

Automated external defibrillators are now available over-the-counter, without a prescription. The question is whether you really need your own automated external defibrillator. Take a critical look at the pros and cons of AEDs before spending the money. Then you and your doctor can decide if it's worth having the device in your home.

An automated external defibrillator is a portable device that senses your heart's rhythm during cardiac arrest and, in some cases, delivers an electric shock to get your heart beating again.

Cardiac arrest most commonly occurs when your heart's electrical activity becomes disrupted and the heartbeat becomes overly rapid (ventricular tachycardia) or chaotic (ventricular fibrillation). Because of this irregular heart rhythm (arrhythmia), your heart stops beating and can't pump blood.

During cardiac arrest, your brain and other vital organs quickly become starved of blood and the life-sustaining oxygen and nutrients it carries. You could die within a few minutes, or if you survive, you may sustain permanent damage to your brain and other organs. The sooner your heart's rhythm is restored the better, since each minute is critical to determining your chance of survival and how much damage you might experience.

If an automated external defibrillator is on hand, a bystander could grab it and easily connect it to your chest to evaluate your heart rhythm. If your heart rhythm can be treated with an electric shock, the AED automatically sends a current to your heart muscle. That jolt can reset your heart back into a normal rhythm, possibly saving your life.

Although cardiopulmonary resuscitation (CPR) is a vital step in the lifesaving process and can keep some blood flowing to your heart and brain for a short time, often only defibrillation can restore the heart's normal rhythm and ultimately save your life.

In addition to being carried by police and ambulance crews, automated external defibrillators are now commonly available in many public places, including malls, office buildings, sports arenas, cruise ships, schools, casinos, airports and airplanes.

The problem, though, is that you're more likely to have cardiac arrest in the privacy of your own home. With an automated external defibrillator in your home, you wouldn't lose precious minutes waiting for rescue workers to arrive with an AED.

The Food and Drug Administration (FDA) approved the first over-the-counter AED for home use in late 2004. Because it's over-the-counter, you don't need a prescription to buy it. The only automated external defibrillator approved for home use without a prescription is the Philips HeartStart Home Defibrillator. The HeartStart AED can be used on children as young as 9 who weigh at least 55 pounds.

The home AED comes with a short instructional training video that shows you how to use and maintain the device.

In an emergency, the automated external defibrillator essentially makes the decisions for you. It offers step-by-step voice instructions to guide you through the defibrillation process. It explains how to check for breathing and a pulse and how to position electrode pads on the person's chest.

Once the pads are in place, the AED automatically analyzes the person's heart rhythm and determines if a shock is needed. If it is, the machine tells you to stand back and instructs you to push a button to deliver the shock. It will also guide you through CPR. The process can be repeated as needed until emergency crews take over.

The FDA's approval of automated external defibrillators that can be used in your home without a prescription has not come without debate.

Proponents of in-home automated external defibrillators say putting them where they're most needed will save thousands of lives each year. If you collapse from cardiac arrest, a family member or friend could quickly grab your home AED, send a jolt of electricity to your heart and, in theory, save your life.

But critics worry that some people may give up a healthy lifestyle, feeling falsely confident that if something happens to their heart, a defibrillator will save them. Critics also fear that people won't call for emergency medical services at all or quickly enough, that they won't maintain their AED properly, or that they'll forget where it's stashed.

For its part, the American Heart Association supports doing away with the prescription requirement for automated external defibrillators. However, the organization says there's not enough information available yet to actually recommend for or against using AEDs in the home. A large clinical trial currently studying home AEDs may provide some answers, but the trial won't conclude for several more years.

Until then, how do you decide if you should buy an automated external defibrillator for your home? Is an AED, as some advertisements suggest, just one more essential safety device, like a fire extinguisher or smoke alarm, that everyone should have in their home?

There's no specific list of criteria to decide if an automated external defibrillator would be appropriate for your home. But here are some things to keep in mind as you consider whether to buy an automated external defibrillator for your home:

• Your risk of sudden cardiac death. Your doctor can help you understand if you or a family member has a condition that may put you at higher risk of cardiac arrest or if you're leading a lifestyle that could cause heart problems. Remember that AEDs work only for cardiac arrest that involves specific types of heart fibrillation. It will not revive everyone in cardiac arrest. And with certain types of heart disease, you may need a defibrillator that's actually implanted in your chest instead of an external device for emergencies.
• Your living arrangements. If you live alone, an automated external defibrillator will be of little use if you experience cardiac arrest — there won't be anyone to use the machine on you.
• Your physical abilities. You or a family member must have the flexibility and strength to sit or squat on the floor, use the device, and get back up.
• Your costs. Automated external defibrillators can be expensive, costing about $1,500. Health insurance doesn't generally pick up the tab.
• Your overall health and philosophy. If you have numerous medical problems, a terminal illness or a very weak heart that has not responded to treatment, you may decide that you wouldn't want to be resuscitated from sudden cardiac death.

If you decide to get an automated external defibrillator for your home, with or without your doctor's approval, make sure you learn how to use it and maintain it properly. If you don't, an AED will be of little use in an emergency.

Here are some tips for your automated external defibrillator:

• Don't rely only on instructional material provided with the AED. Enroll yourself and your family members in a community education course to learn how to use your automated external defibrillator properly. This will also allow you to come to the rescue if someone experiences cardiac arrest in a public place and there's an AED nearby.
• Take the automated external defibrillator to your doctor's office and demonstrate how you and your family would use it, to make sure you're using it correctly.
• Have a family practice run using the automated external defibrillator as you would in an actual emergency. Remember, the AED works only on certain types of cardiac arrest. Know what steps to take if the AED indicates a shock isn't needed but the person remains unresponsive.
• Review your automated external defibrillator instructional material every three to six months to make sure you remember how to use the AED.
• Store your automated external defibrillator in an easily accessible place and make sure all family members know where it is. Be careful if you take it with you on outings, such as shopping or dining — you risk damaging or losing it.
• Keep the automated external defibrillator maintained properly, including installation of new batteries as needed.
• Learn CPR. Take a course to learn the signs of cardiac arrest, how and when to summon emergency responders and how to perform CPR.
• Only the Philips HeartStart Home Defibrillator is available without a prescription. Other brands require a prescription because the FDA hasn't found that they can be used safely and effectively by a layperson without formal training. Prescription AEDs are not intended for home use, but rather for use by emergency crews or for installation in public places. Don't be lured by unscrupulous Web sites or other sellers offering other AEDs without a prescription.

Automated external defibrillators offer a way to save someone's life, perhaps your own. But they may not be suitable for everyone's home. Before buying one, talk to your doctor and do a little research. And don't forget to learn the basics, like CPR.