Sudden Death: Exercise Should Not Be Blamed For Cardiac Death, Study Suggests

TORONTO - The stories are always shocking: A young, often super fit teenager or young adult drops like a stone during an athletic event, dead before they hit the ground.

The obvious incongruity of sudden cardiac death in an athlete perplexes the public and alarms parents of young sportsmen and sportswomen, who may see their own children in the lifeless bodies of the stricken.

A new Canadian study may relieve some of those concerns. It finds that the majority of sudden cardiac death cases don't happen during exercise, at least in young adults.

In fact, the highly visible deaths of athletes — or the deaths averted because of rapid resuscitation, as in the cases of former NHL player Brett MacLean or Premier League footballer Fabrice Muamba earlier this year — are the exceptions. Most sudden cardiac deaths happen off the field of play, among people who are not exerting themselves.

That's important to know, not just because of the relief it may provide some parents. Targeting heart resuscitation equipment — such as automated external defibrillators or AEDs — at sporting events probably isn't the best use of the resources, says Dr. Andrew Krahn, a cardiologist in the medical school of the University of British Columbia and one of the authors of the study.

"If we're going to try to prevent this problem, we need to be aware that the problem is not a sports problem. The problem is really an infrequent but tragic death that happens usually at home and usually at rest," says Krahn.

"Putting it (an AED) at the Y is a sensible thing to do, but not at the exclusion of putting it at the mall. Or the school."

The study is being presented Monday in Toronto at the Canadian Cardiovascular Congress, a scientific meeting co-hosted by the Canadian Cardiovascular Society and the Heart and Stroke Foundation.

The findings suggest training people in CPR (cardiopulmonary resuscitation) and making AEDs available in more public places could save more people from sudden cardiac deaths, says Dr. Beth Abramson, a Toronto-based cardiologist and researcher funded by the Heart and Stroke Foundation.

"Our goal is to make AEDs as available as fire extinguishers in public places from Yellowknife to St. John's," Abramson said in a statement. "The odds of surviving a cardiac arrest can increase to up to 75 per cent when early CPR is used in combination with an AED in the first few minutes."

She notes the importance of a rapid response was demonstrated this summer when MacLean suffered a cardiac arrest while playing a pick-up hockey game in Owen Sound, Ont. Players performed CPR and a spectator ran for the arena's AED. MacLean survived, though his professional hockey career is over.

Krahn, who until recently lived in Toronto, worked with colleagues to identify cases of sudden cardiac death among coroners' reports in Ontario. They looked at 174 presumed cases that occurred in 2008 in people aged two to 40. (Sudden cardiac death doesn't happen exclusively to the young, but for the purpose of the study the researchers wanted to focus on children and young adults.)

Up to 40,000 Canadians of all ages die of sudden cardiac arrest each year, according to the Heart and Stroke Foundation. Krahn says the Ontario numbers suggest that nationwide about 500 to 700 young people die this way each year.

Three-quarters of the sudden cardiac death victims in Krahn's study were between the ages of 18 and 40. And the majority of the deaths — 72 per cent — occurred at home. Only nine per cent of the adult deaths occurred during moderate or vigorous exercise.

Krahn says the work suggests that most people who die of sudden cardiac death are like his brother-in-law, who died while reading a book. He was found in his chair, the book still in his lap.

"He made no attempt to try to seek help. And that's because presumably the symptoms are so rapid that by the time you say 'I don't feel well. Something's wrong,' you're done. It's virtually instantaneous," Krahn says.

Krahn says the numbers in children and teens younger than 18 were small, too small to rule out the possibility that exertion might play a role in sudden cardiac death in this group. That doesn't mean the researchers think it does, only that they cannot say with confidence that it does not. They are doing a follow-up study looking at sudden cardiac deaths in children over five years to see if they can answer the question.

He suggests cases like MacLean's draw a lot of attention, and that attention creates the impression that sudden cardiac death is brought on by athletic exertion. But people don't see the many more cases, like his brother-in-law, that are actually the norm. Those are probably often written off as heart attacks.

In fact, many people confuse sudden cardiac deaths with fatal heart attacks, but the terms are not synonymous. Heart attacks are caused by blood clots in the heart muscle. Sudden cardiac death occurs when the rhythm of the heart goes haywire, stopping the heart from pumping blood.

"In lay terms it's a wiring problem, not a plumbing problem," Krahn says.

"The lay perception that is quite common is that the heart stops. But in fact typically what happens is it beats so rapidly and chaotically that it can no longer pump blood. It doesn't have time to fill and empty properly."

The term for the dangerous rhythm is ventricular fibrillation. When it happens, there's little time to react.

"The issue is if you go into fibrillation, you have somewhere between five and 10 seconds to call for help. In effect, if your heart stops pumping blood, that's how long you have until you're out."

If someone is around to call for help and begin resuscitation — especially if there is an AED available — people can be brought back. But the younger the person, the more likely they are to be able to tolerate the period without oxygen and still recover. Krahn says people 50 and older rarely survive.

Krahn runs a clinic where he works with survivors of cardiac arrest. He also tests family members of people who have had a cardiac arrest. While medical science doesn't know all the things to look for to determine who is at risk of sudden cardiac death, some risk factors are know. And it is known the risk runs in families.

For instance, people with Long QT syndrome, a heart rhythm disorder, are at greater risk. Krahn says testing can check for electrical abnormalities in the heart.

People identified to be at higher risk of sudden cardiac death can be treated with drugs —beta-blockers and others — and in some cases may need to have an implantable defibrillator, a device like a pacemaker, which monitors the heart and when necessary restores normal rhythm by delivering small electric shocks.

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