What is a cardiac arrest?

Many people think a cardiac arrest is the same as a heart attack, but they’re two distinct emergencies.

In a cardiac arrest, the heart’s electrical system fails, causing the organ to suddenly stop beating and unable to pump blood to the brain, lungs and other parts of the body, according to the American Heart Association. A person becomes unconscious within seconds, no longer has a pulse and stops breathing. Starved for oxygen, brain cells start dying quickly and many people who do survive a cardiac arrest end up with brain damage.But the odds of surviving are slim: Four out of five cardiac arrests happen in the home, and more than 90 percent of the victims die before reaching the hospital, according to an Institute of Medicine report. Indeed, Petty went into cardiac arrest at his home in Malibu and was taken to UCLA Medical Center, but couldn't be revived.To keep a victim alive, help must come immediately: Starting CPR right away can keep the blood flowing until paramedics arrive. The best bet is a defibrillator that can shock the heart back into a normal rhythm. But even if their heart is revived, some patients will remain in a persistent vegetative state if their brain was injured due to the lack of oxygen.Possible causes of sudden cardiac arrest include coronary heart disease, physical stress, and some inherited disorders, the National Institutes of Health notes. But there’s sometimes no clear cause.

Most heart attacks — which happen when a blockage stops blood flow to the heart — don’t lead to sudden cardiac arrest, the AHA says. The heart usually keeps beating and the person remains conscious, but the blockage must be treated within a few hours to prevent the heart muscle from dying, the NIH notes. Heart attack symptoms can also appear suddenly, but many patients feel warnings signs in the hours or days before the emergency. A cardiac arrest, on the other hand, often happens without warning.More than 6 million people in the world  have a heart attack each year, compared to about  3 million who suffer a cardiac arrest.