Warning signs of sudden cardiac death are often missed or misdiagnosed

By John Murphy, MDLinx
Published October 26, 2015

Key Takeaways

Fainting and near drowning events may actually be warnings of sudden cardiac death, according to researchers who presented their results on October 25, 2015 at the annual congress of the South African Heart Association, held in Rustenburg, South Africa.

Such events are often dismissed or misdiagnosed. But they may be due to long QT syndrome (LQTS), said presenter Paul Brink, MBChB, MMed, PhD, professor of internal medicine at Stellenbosch University in Tygerberg, South Africa.

“LQTS is a cardiac disorder associated with blackouts (syncope). It is a treatable cause of sudden death but unfortunately blackouts, being common and most often not serious, are often ignored and the small group with serious events are then missed,” Dr. Brink said. “When presenting to medical services, the underlying cause may also be misdiagnosed.”

In this study, researchers screened relatives of 26 LQTS index cases and identified 203 living patients with the KCNQ1 A341V mutation in South Africa. This mutation has been traced to a common founder couple of Dutch descent in the early 18th century.

The researchers determined that 4 in 5 (79%) of the mutation carriers had experienced syncope. Only 26% of the patients had been diagnosed with LQTS initially and given appropriate treatment, while 40% were incorrectly diagnosed with epilepsy, and 34% were given incorrect explanations such as drowning or sick sinus syndrome.

“Our research shows that many patients with LQTS never see a doctor, or when they do, they are given an inaccurate diagnosis,” Dr. Brink said. “The most common misdiagnosis in living patients was epilepsy, while in those who died it was drowning.”

Of the 203 patients identified, 23 died before age 20. Half of these “drowned” despite being able swimmers, the researchers reported. A 13-year-old girl died on a skating rink while being treated for epilepsy, and a 5-year-old boy “choked on water.”

“The most feared consequence of LQTS is death during a blackout,” Dr. Brink said. ”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.”

Dr. Brink said that he is astonished that so many patients don’t take blackouts seriously and don’t seek medical attention for such episodes. “And to make matters worse, people frequently do not realize that death during a blackout is a harbinger of similar risk to surviving relatives,” he said.

Furthermore, doctors must correctly diagnose such patients, Dr. Brink said. “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,” he said. “Sudden deaths can be prevented if people recognize unusual fainting events and take action.”

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