Bloomberg News Michael Jackson CDs for sale in Tokyo Pop star Michael Jackson’s passing is another reminder about how sudden and unexpected cardiac arrest — the believed cause of Jackson’s death at age 50 — can be. About 300,000 Americans die of sudden cardiac arrest outside the hospital each year, according to the American Heart Association . Around this time last year, Tim Russert , the host of TV’s “Meet the Press,” died from a heart attack at age 58. But heart attacks aren’t synonymous with sudden cardiac arrest; they are but one trigger, according to Forbes.com . In fact, most sudden cardiac deaths aren’t caused by clogged arteries, but instead by cardiac arrest, or a disruption in the heart’s electrical rhythm, which causes a trembling of the heart ventricles rather than a normal contraction. The arrhythmia limits the amount of blood that circulates and death can occur if the condition continues for more than a few minutes. Some 95% of those with sudden cardiac arrest die, according to the National Heart Lung and Blood Institute . The heart can be potentially be restarted with a defibrillator if action is taken quickly, according to NHLBI. Reuters also has a Q&A on cardiac arrest and here is a 2004 WSJ interactive graphic with info on cardiac arrest and defibrillators. Individuals

with damage to their hearts are at particular risk for sudden cardiac arrest. The causes of the damage could be past heart attacks, genetic factors or substances such as cocaine and ephedrine, which is sometimes found in weight-loss supplements, according to Bruce Lindsay , past president of the Heart Rhythm Society and current head for Cardiac Electrophysiology and Pacing at the Cleveland Clinic. The best way to identify people at risk is to measure their “ejection fraction,” the amount of blood squeezed out with each heart beat, Lindsay told the Health Blog. Normally the figure in in the range of 60% to 70%, but in people with heart damage, it could be as low as 30%. Warning signs for heart disease include shortness of breath or chest pain, and people suffering from these symptoms should see their doctors, said Lindsay. “These are things that are, in part, preventable,” he said. “If we recognize them and treat them we can save lives.” The Los Angeles coroner’s office is conducting an autopsy of Jackson, but results won’t be final for a while as toxicology tests are completed. An office representative told the Health Blog that the coroner plans to issue an update later this afternoon.

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After Jackson’s Death, Tracking Causes of Sudden Cardiac Arrest