This is significant because Long QT Syndrome runs in families -- and the fear of death is only heightened when a relative dies. It had been thought that the death of a family member meant a greater risk of sudden death to parents, siblings or children in that same family.
The new findings are reported in today's issue of Circulation, the journal of the American Medical Association, by the world's leading expert on the disorder, Arthur Moss, M.D., director of the Heart-Research Follow-up Program at the University of Rochester Medical Center. Moss is senior author of the study.
A clinical study of about 800 people with Long QT from approximately 200 families showed that an individual's own characteristics, such as being female, coupled with the findings on an electrocardiogram (ECG), are the major determinants of risk for sudden death. For example, two sisters with the same genetic defect for Long QT Syndrome can have different ECG patterns and very different risks for sudden death.
"This was a surprise," says Moss, professor of medicine and head of the International Registry for Long QT Syndrome that tracks more than 5,000 patients worldwide. "We used to think the risk of sudden death ran in families. But now we know that just because one family member experiences a life-threatening event, it doesn't mean that other family members are at high risk for the same fate. Each individual within a family with Long QT needs to come in and get evaluated."
Long QT Syndrome afflicts about 25,000 Americans; about 1,000 people with the disorder die unexpectedly each year. Sudden death in these patients can occur during an adrenaline rush, such as playing an exciting sports game or getting emotionally upset over bad news. It can result in the death of even very young, otherwise healthy people -- and it is the leading cause of sudden death among adolescents.
Patients with Long QT Syndrome have abnormally long intervals in the electrical recovery period (QT interval) after each heart beat. During times of excitement or stress, the heart can beat very fast, and in people with Long QT the electrical activity of the heart muscle does not recover completely before the next heart beat. This incomplete recovery at fast heart rates is dangerous. Current treatment centers on medications that block the effects of adrenaline, thus preventing fast heart rates.
Earlier research by Moss and his colleagues identified defects in three specific genes that cause Long QT. Moss is also credited with developing the International Long QT registry, the first such "disease registry" in the world that tracks patients and enables physicians to develop strategies to prevent sudden death. The aim of the latest study was to determine if the risk of sudden death was similar among close relatives with the same gene defect.
The findings from this genetic disorder, Moss says, provide important insights into the risk of death from common health problems such as heart attacks and hypertension, which also run in families.