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Without Treatment, Cardiac Arrest Kills Quickly

The circumstances surrounding Michael Jackson's death are not entirely clear. But appearing before the news media Thursday, Jackson's brother, Jermaine, said it's believed Michael Jackson had cardiac arrest, though the cause of death won't be known until an autopsy is performed. Here's some background:

Question: What is a cardiac arrest?

Answer: It's when the heart suddenly stops, which can happen for dozens of reasons, from underlying heart disease to a drug overdose, choking or trauma, says Cam Patterson, chief of cardiology at the University of North Carolina-Chapel Hill.

Victims lose consciousness, stop breathing and lose their pulse and blood pressure.

At most, about 20 percent of people who go to the hospital for cardiac arrest survive, Patterson says. Someone is much more likely to survive if he is revived with a defibrillator right away.

Tim Russert, host of NBC's "Meet the Press", died last year of cardiac arrest.

Q: Is cardiac arrest the same as a heart attack?

A: No. A person who has a heart attack - which results when blocked blood flow causes damage to the heart muscle - may still be able to walk and talk, Patterson says.

These patients need to quickly have their blood flow restored, such as through angioplasty, when doctors thread a balloon into a blood vessel.

Q: What causes cardiac arrest?

A: The most common cause is heart disease, the leading cause of death for a 50-year-old man, Patterson says.

Heart disease or previous heart attacks can weaken the heart, says Jeanne Poole, a professor of medicine at the University of Washington.

The damage can result in an abnormal, rapid heart rhythm, which can be fatal.

Though some people have a genetic abnormality that puts them at risk for these fatal rhythms, they make up only 5 percent of cases, Poole says.

Severely abnormal electrolytes, possibly caused by extreme dieting or fasting or rare hormone problems, also can cause such fatal heart rhythms, Poole says.

Another possible cause is primary respiratory arrest, when the person stops breathing, Poole says. That can be caused by blood clots in the lungs, severe underlying lung disease or possibly drug overdose.

Q: What might have happened in Jackson's case?

A: Jackson most likely had ventricular fibrillation, an electrical disturbance of the heart that occurs when the heart begins beating 400 to 500 beats per minute - much more than the normal 70 to 75 beats, says Douglas Zipes, emeritus professor at Indiana University School of Medicine and past president of the American College of Cardiology.

"When you look at the heart in ventricular fibrillation, it looks like a bag of squiggly worms," Zipes says. "The contractions are totally ineffective ... Therefore, no blood is pumped to the brain, causing him to black out.

"The heart's pacemaker is the sinus node," Zipes says. "It is the conductor of the orchestra, coordinating the heart's electrical rhythm. When all the instruments are playing in a coordinated manner, the result is music. In ventricular fibrillation, it's as if the orchestra is warming up and what you hear is cacophony."

Q: What can you do for someone in cardiac arrest?

A: Sudden cardiac death occurs within minutes unless someone gets the heart working again, either through CPR (cardiopulmonary resuscitation) or with a defibrillator, which uses an electrical shock to get the heart pumping correctly.

Brain death begins to occur in just four to six minutes, so restarting the heart quickly is vital, the heart association says.

CPR can buy victims time until they can be shocked with a defibrillator, says Abhi Mehrotra, assistant professor of emergency medicine at UNC-Chapel Hill. By compressing the chest, rescuers circulate blood and get oxygen to vital organs such as the brain.

A victim's chances of survival go down 7 percent to 10 percent every minute that passes without CPR and defibrillation. Few people are revived after 10 minutes, the heart association says.

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