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Diagnosis of genetic heart rhythm disorder, long QT, life-changing for families

11/05/2014 05:45 EST | Updated 01/05/2015 05:59 EST
TORONTO - When Katherine Dines was ready to start a family, she wanted to make sure there wasn't something lurking in her genetic makeup that could threaten the health of her children. She had good reason: her mother and maternal grandmother had both died suddenly in their early 20s. And no one knew why.

Her mother had experienced numerous fainting spells, and doctors had diagnosed her with epilepsy. She died when Dines was just four months old.

"I always had a feeling there was something, but every doctor I talked to always said the same thing: 'Oh, no, it's just a fluke. There's nothing to be worried about,'" said Dines, a radio station host in Ottawa. "I decided, 'OK, I guess that's the way it is. I'll just start my family.'"

But when her first daughter, Sydney, was about three and she was expecting her second child, a cousin who worked at the Children's Hospital of Eastern Ontario (CHEO) showed a cardiologist the autopsy report on Dines's mother. He suggested Sydney be brought in for an electrocardiogram, or ECG.

"He diagnosed her on the spot after reading the ECG, which floored me," recalled Dines.

Sydney had long QT syndrome, a genetic heart rhythm disorder that can cause fainting spells, seizures and, in some people, fatal cardiac arrest.

Genetic testing showed Dines also had the condition and, after her birth, daughter Grace also was diagnosed with long QT. If one parent carries a mutation that causes the disorder, each child has a 50-50 chance of inheriting the flawed gene.

Those with the syndrome have structurally normal hearts, but there's a problem with the electrical impulses that pass through the heart, which can cause it to beat erratically, explained Dr. Robert Gow, a CHEO cardiologist who specializes in electrical heart rhythm disorders.

"Under certain ... circumstances, chaotic rhythms can be set up in the heart, which makes the heart beat very quickly and that's when children would either faint or people would have a cardiac arrest and die," said Gow, estimating that 15 to 20 per cent of unexplained cardiac deaths among people with no evident heart disease on autopsy may have had undiagnosed long QT syndrome.

Many Canadians may be unfamiliar with the disorder, which was in the news earlier this week when CHEO filed a court challenge aimed at invalidating patents on human genes. The hospital is using long QT genes as a test case, in the hope a favourable ruling would set a precedent on any human DNA patents.

Long QT refers to a reading on an ECG, which measures five types of waves. The interval between the Q and T waves shows electrical activity in the heart's lower chambers, corresponding to the time it takes for the heart to contract and refill with blood before the next contraction. With long QT syndrome, that interval is abnormally prolonged.

Gow said an estimated one in 2,000 to 2,500 Canadians is born with long QT syndrome; about 15 mutated genes have been identified, with one of three of these genes accounting for the syndrome in most families. It's estimated that at least 10 per cent of babies who have died of sudden infant death syndrome, or SIDS, may have been affected by long QT.

While the condition can be managed with drugs called beta blockers, which regulate and slow the heartbeat, and sometimes an implanted defibrillator to restart the heart, Gow said learning that long QT is part of a family's genetic makeup can be devastating.

"We change people's lives sometimes with these diagnoses, and depending on individual risk profiles, it affects people differently."

Dines, 46, said she and her daughters, now 15 and 12, have had to restrict their physical activity, and managing stress is also critical as that can trigger an episode.

"It was life-altering," she said of the diagnosis. "My kids, they're not supposed to play competitive sports ... we have to let people know they have the condition, they wear MedicAlert bracelets." There's also a portable defibrillator in their home.

"It's scary because you can't be with your kids 24-7. As they grow up, you want them to have as normal a life as possible. And to look at them, you wouldn't know they had a heart condition ... I don't want them to be fearful of it, but it is challenging."

Still, knowing long QT runs in one's family is better than not knowing, said Pam Husband, executive director of the Canadian SADS Foundation. SADS is the acronym for sudden arrhythmia death syndromes, one of which is long QT.

Husband didn't know long QT ran in her former spouse's family until the sudden death of her 16-year-old son Greg in 1990. He died in bed and was found by his father in the morning.

Why his heart stopped was a mystery, though she later learned his was a classic case of long QT syndrome.

"My son had years of symptoms. He fainted from the alarm clock in the morning, from midway rides, from being startled in various ways," said Husband of Mississauga, Ont. "And he was misdiagnosed with idiopathic epilepsy (of unknown cause).

"There is an element of almost science fiction attached with some of these sudden cardiac deaths because we just don't expect them in young people. And when you tell someone that a person died because the alarm clock went off in the morning or the window slammed in the middle of the night or a phone call startled them, it sounds like horror on Elm Street or something."

Husband said it took a year and a half before her son's death was attributed to long QT syndrome, when her daughter, now 38, was diagnosed, based on ECGs and other tests. DNA sequencing did not pick up any mutations known to cause long QT, so the genetic underpinnings are still a puzzle.

"It is basically overwhelming and it has a huge impact on a family in terms of their sense of safety after the fact — for their children, for themselves, for their extended family," she said. "And it's difficult for people to come to terms with."

For Susan Edwards, there was no choice: her introduction to long QT couldn't have been more dramatic.

While waiting to be discharged from her local hospital after having her appendix removed, the Oshawa, Ont., mother of two suffered a full cardiac arrest; it took 45 minutes for the code blue team to restart her heart, and she had three more arrests over the next six hours while in the critical care unit.

"I was 29, I was perfectly healthy, I was in amazing physical shape, very athletic. And they had nothing to go on," recalled Edwards, now 36.

She was transferred to a Toronto hospital, where she was diagnosed with long QT, put on beta blockers and implanted with a defibrillator to shock her heart if she goes into cardiac arrest.

While her father and sister were also diagnosed with the syndrome, based on ECG and other tests, it's not so clear-cut for her children.

The gene causing her condition is still to be identified, meaning they don't know if they too are affected (in some cases, ECGs can look normal).

"They were really put in a bubble at first ... but you get to the point where you have to break the bubble a little bit. You have to let them be kids," said Edwards, who has to limit their physical activities, just in case.

Her daughter, 10, gave up dance classes and now horseback rides; her son, a naturally gifted hockey player, can only play on non-competitive teams.

"He just turned eight and he's at that age where it's 'Why can't I?'" she said. "At this point, you're not letting him do something further that he's great at for the chance he has it. But he may not have it."

Edwards admitted she often feels like a ticking time bomb — and that her kids may be too.

"I'll never be OK with it. I have my days where I cry. I have my days where I'm really angry. But I'm so, so lucky that I survived it."

Yet her kids' bedtime can spark feelings of anxiety, she said. "I never, ever say, 'See you in the morning.' I never like to promise them anything I can't guarantee.

"When I go to bed at night, that's something that really scares me, that I'm not going to wake up."

Follow @SherylUbelacker on Twitter.

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Online: www.sads.ca

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