People who experience frequent blackouts and near-drowning incidences may be at increased risk of a heart disorder known as long QT syndrome, which can raise the risk for sudden death, according to new research.

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Researchers say frequent blackouts can be an indicator of LQTS, raising risk of sudden death.

Prof. Paul Brink, of the University of Stellenbosch in Tygerberg, South Africa, and colleagues recently presented their findings at the South African Heart Association annual congress in Rustenburg.

Long QT syndrome (LQTS) is a rare disorder characterized by fast, erratic heartbeats, which can cause blackouts or seizures. It is estimated that around 1 in 7,000 people in the US have LQTS, and the condition is responsible for around 3,000-4,000 deaths in the country every year.

The condition is most commonly inherited, caused by mutations in genes that control the production of specific ion channels in the heart. These mutations can disrupt the flow of sodium ions or potassium ions through the ion channels in heart cells, causing an uncontrollable heart rhythm.

LQTS can be treated with a number of medications, such as beta-blockers, which can help slow the heart rate. A pacemaker or surgery to remove specific nerves in the body’s sympathetic nervous system may also be treatment options.

Despite being treatable, however, Prof. Brink notes that LQTS is often ignored or misdiagnosed as other conditions that involve blackouts and seizures, such as epilepsy or panic attack, which can prove fatal.

For their study, the team set out to gain a better understanding of the frequency of misdiagnosis and missed treatment opportunities among people with LQTS.

By screening the relatives of 26 individuals in South Africa with LQTS, the researchers identified 203 living people with a KCNQ1 A341V mutation, commonly found among people diagnosed with the heart disorder.

Fast facts about LQTS
  • Around 50% of people with LQTS experience their first abnormal heart rhythm by the age of 12
  • LQTS is rarely diagnosed after the age of 40
  • Women are more likely to develop LQTS than men.

Learn more about irregular heartbeat

Of these individuals, 70% reported having experienced blackouts, yet only 26% had been diagnosed with LQTS and received the appropriate treatment.

Of the remaining individuals with a KCNQ1 A341V mutation who experienced blackouts, 40% had been incorrectly diagnosed with epilepsy, while 34% were given other inaccurate explanations for their symptoms, such as sick sinus syndrome.

The researchers identified 23 individuals who died before the age of 20, half of whom “drowned” despite being able to swim. One death involved a 13-year-old girl who, while being treated for epilepsy, died on a skating rink, and another death involved a 5-year-old boy who “choked on water.”

The researchers say their findings highlight the large proportion of people with LQTS who ignore blackouts and fail to see a doctor.

“The most feared consequence of LQTS is death during a blackout,” says Prof. Brink. “But a lot of patients do not see a doctor after a first fainting spell, or even subsequent ones. They faint, lie on the ground for a minute or two, wake up and go on with normal life. They may even see alternative medicine practitioners for these seemingly innocuous events.”

However, the team’s findings also show that even when patients with LQTS do visit a doctor, they are frequently misdiagnosed. “An incorrect diagnosis of epilepsy, panic attacks or vasovagal syncope when the problem is an underlying arrhythmia disorder leads to inappropriate management and may be detrimental,” notes Prof. Brink.

Based on their results, the researchers call for people to take frequent fainting seriously. Prof. Brink adds:

Sudden deaths can be prevented if people recognize unusual fainting events and take action. Fainting at the sight of blood is harmless but a blackout during activity is cause for further investigation. The same goes for drownings or near drownings. If someone suddenly stops swimming during a competition and floats lifeless, this is obviously not a typical drowning.”

Last month, Medical News today reported on a study in which researchers suggested sleep apnea could be misdiagnosed as depression.