The problem is similar to a heart condition called long Q-T syndrome that contributes to sudden death in young people and adults. In long Q-T syndrome, the heart electrically recharges itself too slowly or in a disorganized fashion in preparation for the next heartbeat, says lead author Michael J. Ackerman, M.D., Ph.D., an assistant professor at the Mayo Clinic in Rochester, Minn. When combined with a trigger, such as intense emotion or physical exertion, a long Q-T heart can go out of control and cause cardiac arrest and sudden death.

"This often explains cases in which children die suddenly while playing in the sandbox, teen-agers die of unexplained drowning, or previously healthy young adults die suddenly while jogging or shoveling snow," he explains.

Cardiac arrest can be fatal within minutes unless the heart's electrical pattern is restored spontaneously or with the aid of a defibrillator, he says.

Current estimates suggest long Q-T syndrome may affect as many as one in 5,000, says Ackerman.

According to U.S. Vital Statistics, about 3,000 infants die each year of SIDS, defined as the sudden and unexplained death of an infant less than one year old. Several possible causes or triggers have been suggested for SIDS, including babies sleeping on their stomachs, nervous system problems related to breathing, abnormal metabolism in the liver and flaws in the heart's electrical channels, he says.

The electrical or ion channels are proteins critical to orchestrating the electrical signals that prompt the heart to squeeze (beat) and refill between each heartbeat, says Ackerman, who is also director of the Mayo Clinic's sudden death g
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Contact: Carole Bullock
carole.bullock@heart.org
214-706-1279
American Heart Association
19-Nov-2002