Do Sudden-Death Genes Strike Women Most?

Women are more likely than men to carry -- and to pass on -- mutant genes that cause long-QT syndrome, a defect in the heart's electrical system linked to sudden death, according to new research.

Long-QT syndrome is a cause of sudden deaths seen in young athletes.

Women are more likely than men to be diagnosed with the problem.

But do they really have long-QT syndrome more often than men? Medea Imboden, PhD, of the French scientific organization, INSERM, and a team of European researchers set out to find the answer.

They studied families with the two most common forms of long-QT syndrome, each one caused by a specific gene mutation.

Long-QT syndrome is named after part of the wave pattern seen on an electrocardiogram.

When it contracts, the human heart sends out an electric signal. On an electrocardiogram, this signal makes a wave pattern.

A different letter identifies each part of the pattern. The part of the signal between Q and T -- the QT interval -- measures the activation and inactivation of the lower chambers of the heart.

People with too-long QT intervals seem healthy but are actually susceptible to dangerous heart arrhythmias (abnormal heart rhythm). Without emergency treatment, such an arrhythmia can lead to death within minutes.

Imboden's team found the genes that cause this problem are more likely to be passed to daughters than to sons -- and that women are more likely than men to pass the genes to their children.

Among children in the study who inherited the long-QT genes, 55% were girls; 45% were boys.

Among children who inherited the gene, 62% got it from their mothers; 38% got it from their fathers.

"The skewed segregation of the mutation from mothers to their daughters might contribute substantially to the observed female predominance in the long-QT syndrome," Imboden and colleagues conclude.

The reason for the unequal transmission of long-QT syndrome genes isn't known.

Imboden and colleagues report their findings in The New England Journal of Medicine.

SOURCES: Imboden, M. The New England Journal of Medicine, Dec. 28, 2006; vol 355: pp 2744-2751.