Sudden cardiac death (SCD) is the largest cause of natural death in the United States claiming about 325,000 adult lives per year.

What makes SCD tragic is it usually affects people in their mid-30s to mid-40s, those who are still starting their family, and the victim's death can have devastating impact on the lives of those they leave behind.

Unlike when it strikes older people who may experience prior symptoms such as chest pain, death also often just strikes young people without any warning signs. It also strikes seemingly healthy people. Fit young athletes, for instance, just drop dead in the basketball court or football fields.

Now a new study published in the New England Journal of Medicine helps shed light on SCD, which can potentially help reduce incidents of such unexpected deaths.

Chris Semsarian, from the University of Sydney, and colleagues investigated 490 cases of SCD that occurred between 2010 and 2012 and found that most of these deaths were linked to coronary artery disease, inherited cardiomyopathies, myocarditis and aortic dissection.

Forty percent of the cases, however, were unexplained so Semsarian and colleagues conducted blood testing and clinical screening of the victims' family members.

The researchers found that while the highest incidence of SCD occurs among 31- to 35-year-olds, the highest incidence of unexplained SCD occurs among those in the 16- to 20-year-old group. Most SCD causes also happened during sleep or rest.

They also found that 27 percent of those who died from unexplained sudden cardiac deaths had clinically relevant genetic mutation despite these people having structurally normal hearts

Most of the discovered gene mutation also had a 50 percent chance of being passed on to the next generation but these can be screened.

"If you work out the gene fault that caused the young person to die suddenly you can test the relatives of the individuals for that genetic mutation and if the relative has the same gene mutation then they are at risk of dying suddenly as well," Semsarian said.

The researchers said that findings of their study can potentially save lives by providing existing family members who have risk for SCD with preventive treatment options.

At-risk relatives could be placed on treatments and undergo medical therapies, or they can be implanted with defibrillators inside of their chest wall.

"Pinpointing the underlying cause can save the lives of others and bring some comfort to devastated families, especially when many of these deaths go unexplained," Semsarian said.

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