Research

Edging closer to an answer for sudden death


‘You don’t expect a young person to go to a game of soccer and not come home or go to sleep and not wake up’, said Professor Chris Semsarian to audience members attending one of the most packed sessions at the conference this year.

The acclaimed cardiologist’s early work looking into why sudden cardiac death occurs in the young revealed that around 40% of young people in Australia who die suddenly have no cause identified after a comprehensive post mortem. That was a number Professor Semsarian said he couldn’t accept.

“Parents who have lost a young son or daughter ask you a million questions about what happened but the two questions that every parent asks is: why did my child die suddenly and how can I stop this from happening to my other children? You can imagine what it’s like having to say, we’re really sorry but we don’t know the cause of death”.

Presenting during the session titled inherited sudden arrhythmic deaths, Professor Semsarian said for a long time, doctors just had no way of answering those questions.

“Sudden cardiac death is a tragic complication of a number of different genetic heart diseases but when we talk about it in the young, and by that I mean under the age of 35 years, it’s a tragedy in every way.

“Its unexpected, it occurs often in a healthy individual with no symptoms whose first presentation of an underlying disease is sudden cardiac death. It’s a tragedy for the individual, for the family, and it’s a tragedy for the community as well”.

Over the last two decades there has been an explosion in the understanding of the genetic basis of heart disease. In 2017 Professor Semsarian said there are at least 40 different cardiovascular conditions that are indirectly caused by a fault in a known gene.

He has spent over a decade painstakingly investigating the blood and tissue samples of nearly 500 sudden cardiac death cases – it’s the amount of all sudden cardiac deaths in people aged one to 35 years of age across Australia and New Zealand during a three-year period.

The findings from that study, published in the NEJM in June last year, and which Professor Semsarian said summarises the last 13 years of his life, have huge implications for helping to understanding why young people die suddenly.

The genetic analysis of the unexplained sudden cardiac death cases revealed that, in a lot of cases, variations in mainly arrhythmia and cardiomyopathy genes were involved, which might suggest that patients were either early in their disease of cardiomyopathy or that there might be some other relationship between cardiomyopathy without a phenotype in sudden death.

“The arrhythmiagenic causes are challenging – the problem with these conditions is that they are often silent at death; at post mortem you can’t see the ion channels that are abnormal under a microscope which is why these cases are often recorded as an unexplained cardiac death in a young person.”

In 27% of other unexplained deaths the research also uncovered a clinically interesting relevant cardiac gene mutation for further investigation.

“Not all of these gene variants would directly cause disease but this was our first pass at looking at very strong candidates for disease causation,” Professor Semsarian added.

Other key findings included that more females than males are affected by unexplained sudden cardiac deaths, typically most cases were around 15 years of age and most young people died suddenly in their sleep or at rest and not during or straight after exercise as we’re often led to believe.

He has this advice about managing a sudden death in a young person:

“You exclude the non cardiac death causes you’re left with the cardiac causes they are distributed into ones where there is a definitive cause around 50-55%%.

For the unexplained case – around 40%, in most of those individuals subsequent management involves looking at the family and screening first-degree relatives.

We’ve been able to show that you can get an additional diagnosis in about 12% of families just from clinical screening alone.”

Commenting on the amount of interest the session received he added:

“I think the reason why this room is full of people is because we are all united in our goal to prevent sudden cardiac death in all ages, particularly in the young.”

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