November 27, 2004
Inherited Risks Go Undiagnosed
Inherited heart defects may be killing up to 80 young New Zealanders a year but many deaths go undiagnosed -- putting relatives who carry the faulty gene at risk.
Sudden deaths of healthy, young people are being attributed to drowning, epilepsy or even cot death while the underlying inherited cardiac condition remains undetected.
"It is imperative we try to make sure nobody in the family has the same thing," Skinner said.
There are several inherited heart conditions which are potentially fatal but which may have few or no symptoms, with some causing repeated fainting, blackouts, or seizures.
The best known, long QT syndrome, causes a tiny delay in the heart's electrical recovery after each beat, making the person vulnerable to a fatal arrhythmia in which the brain may be deprived of blood causing sudden death.
"If you've got long QT and you don't know it and you have an unexpected blackout, there is a 50 per cent chance you will be dead within 10 years," Skinner said.
Relatively inexpensive betablocker medication could reduce that risk 10-fold.
More than 20 years ago Claire Guyan's sister Denise, a bright talented 13-year-old, died suddenly during a private swimming lesson. Her death was attributed to drowning. Three years later her brother also died suddenly during a swimming lesson. It was only then that full investigations revealed their mother had long QT syndrome.
Claire Guyan was incredulous that, two decades on, pathologists were not routinely screening sudden deaths for long QT syndrome.
"Twenty-five years ago when my brother and sister died you could explain the ignorance but now I'm really surprised to hear it's not routine," she said. "We could have saved Stephen's life through pretty simple testing."
Pathologists have been asked to save DNA from any case of sudden unexplained death, but Skinner said there was no money to test the samples for genetic conditions.
"Currently, the only way we're going to find out if someone died of long QT syndrome is doing the test in a research lab," he said. "That has to change because it has immediate clinical implications for the whole family."
No-one yet knew exactly how many sudden deaths were owing to inherited cardiac conditions although international studies suggest they probably kill 80 New Zealanders a year.
"Data from the US suggests it is more common than childhood leukaemia," Skinner said. His team was collecting DNA from the Guthrie cards of about 100 sudden infant death (cot death) victims to screen for long QT syndrome. Some studies had shown about 4% of cot deaths were due to long QT.
The Health Ministry's chief public health adviser, Ashley Bloomfield, said the ministry was aware of the research interest, but said there were higher priorities.
"Understanding of QT syndrome is still emerging," he said. "New Zealand, like most other countries, is in the information gathering stage. We don't yet have an accurate indication of the number of people affected by it so we are watching and monitoring the situation."