Richard Musgrove
Dr Richard Musgrove is a zoologist and science journalist. He writes for Cosmos and Double Helix.
Swedish researchers may have helped to prevent premature deaths from Sudden Arrhythmic Death syndrome (SADS). Exploration of a decade-long patient database has revealed what was happening in the lead-up to the sudden unexplained deaths of 900 young people from SADS.
About 32,000 Australians go into Sudden Cardiac Arrest (SCA) each year, Professor Jamie Vandenberg, Head of the Cardiophysiology Unit at Sydney’s Victor Chang Research Institute, told Cosmos.
Fifteen to twenty percent of those are usually under the age of thirty-five and three to four thousand of the total deaths would have been put down to SADS, says cardiologist Dr. Elizabeth Paratz, of Melbourne’s HEART Lab.
The SCA fatality rate is about 90%, she adds.
‘Arrhythmic’, means ‘without rhythm’, referring to a problem with the rate or rhythm of a person’s heart beat, possibly leading to a cardiac arrest, where the heart stops pumping blood. This is not the same as a heart attack, which is when one of the main blood vessels supplying the heart gets blocked. SADS is genetic and an umbrella term covering unexpected deaths in people younger than 40 where the cause of death is inconclusive.
“The heart looks normal at autopsy, without coronary disease, for example, or thickened muscle. So, these people didn’t have heart attacks or heart blockages. They just had an unclear, a totally unclear cause of death, even after comprehensive investigations,” Paratz told Cosmos.
Vandenburg agrees, “those hearts are structurally normal. So, when you do the autopsies, you’re left scratching your head, saying, we don’t know what went wrong.”
“You’ve inherited a mutation in one of the ion channel genes, or other genes that regulate electrical activity, and that’s been triggered, and it’s causing arrhythmia, and it’s caused the death, sure.”
So, what are the signs? Researchers at the Sahlgrenska Academy – University of Gothenburg, Sweden explored a decade-long database of Swedish SCA Deaths to find out.
“SADS has not been well evaluated despite being one of the most common underlying causes of sudden cardiac death in young people, including young athletes,” said lead author Dr. Matilda Frisk Torell .
“We conducted an analysis of a large cohort of cases of sudden cardiac death in Sweden to describe the incidence of SADS and to characterise frequent findings that occurred before death to highlight opportunities for prevention.”
Torell says SADS accounted for 22% of all SCA deaths in Sweden for the 2000-2010 study period.
For that decade, 903 of the Swedish fatalities were under 36, says Torell, most around 23 years old and 64% were male.
The sex difference may be down to testosterone, which does affect the heart, says Vandenburg, as well the tendency, as a generalisation, for boys to be more vigorous in their exercise than girls, particularly acute, sudden bursts, which can trigger SADS in susceptible people, he says, adding that boys also tend to take more risks, whether that be recreational drugs or other potentially triggering activities. “But we really don’t know why boys in most instances”.
Neither Vandenburg nor Paratz were involved in the research.
Those Swedes who died were also 9% more likely to have been hospitalised or visited outpatient visits within 6 months of death; 10-times more likely to have been admitted with fainting spells; and 25-times more likely to have been hospitalised with convulsions.
Slightly more than 1 in 10 had also been diagnosed with arrhythmia; 18% had abnormal electrocardiograms (ECGs); and 52% had palpitations, fainting, nausea and vomiting and signs of infection. Family history was significant, others had been diagnosed with psychiatric conditions, and some had been on psychotropic drugs.
“In the majority of cases, there weren’t red flag symptoms, says Paratz,. “I know they’ve highlighted some like [fainting] and seizure and psychiatric history, but I think it was in about 70% of cases, there weren’t really red flags that anyone would have acted on, which is why this remains such a mysterious entity.”
Australia, is similar says Paratz. “We found that around three quarters of [SADS] people experienced sudden cardiac death at a young age, did not have actionable things beforehand. This did not represent a systematic failure or variations in care. This was just it is a very hard thing to predict, and often the first presentation is the incredibly dramatic one of a cardiac arrest.”
“So, what can we do better in predicting at-risk people and having preventative interventions? That is really the question.”
Screening at-risk young people may be more effective now signs and symptoms preceding SADS are clearer, says Torell, adding, there is still a need to better understand risk factors such as psychiatric disease and treatment, and the potential for other diseases to trigger SADS in genetically-predisposed young people.
The study was presented as a poster at the European Society for Cardiology Preventative Cardiology Meeting in Milan in Italy earlier this month.
Sudden deaths: new way to spot cardiac problems
