By Martha Kerr

CHICAGO (Reuters Health) Nov 19 - Approximately 5% of SIDS cases are the result of long QT syndrome, according to research presented here Tuesday morning at the American Heart Association's Scientific Sessions 2002.

There has been speculation that some cases of SIDS may be the result of fatal arrhythmias. Dr. Michael J. Ackerman of the Mayo Clinic in Rochester, Minnesota, and colleagues, tracked all SIDS cases reported in Arkansas between September 1997 and August 1999. They extracted DNA from tissue obtained from the 93 cases found, looking for evidence of mutations in five genes known to be linked with long QT syndrome.

The investigators found missense mutations in one of the five genes in 27 infants. In four infants (5%), "there was strong evidence of cardiac channelopathy," Dr. Ackerman reported. No evidence of these channel mutations was found in a group of more than 200 healthy controls.

"This 5% could not be due to chance," he commented. "There is a recurrence rate in SIDS, but not like you would see in a hereditary condition such as long QT syndrome, which is an autosomal dominant trait."

Dr. Ackerman pointed out that long QT syndrome is "highly treatable" with beta-blockers or implantable defibrillators, which could potentially be adapted for use in infants.

"Now we can start thinking about neonatal screening," Dr. Ackerman told Reuters Health. A prevalence of 5% translates to approximately 7 SIDS deaths per 1000 per year, or around 2 to 3 times more prevalent than childhood leukemia, he noted.

"We routinely screen for diseases with a prevalence of 1 in 100,000," he pointed out. "A simple 12-lead electrocardiogram could detect long QT syndrome, but we are not to the point where we can recommend that."

These study results should not be used to make screening recommendations, he said "Ultimately, that decision will likely be made less by scientists than by public opinion."

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