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For most patients, sudden cardiac death is completely unexpected, according to Dr. Amit Khera, a cardiologist at Massachusetts General Hospital.
“It’s always particularly devastating because many don’t have prior symptoms. Their first symptom is actually dropping dead,” Khera said. “The question is – can we find these people before something really bad happens?”
Many scientists, including Khera, theorized that one way to find people who might suffer these sudden cardiac deaths — fatal events related to an abrupt cardiovascular failure — could be their genetics.
“We always had a hunch that maybe there was something in their DNA that predisposed them to this tragedy,” he said.
Now, he and his colleagues believe they’ve found 14 different gene variants, spread across seven genes that may put their carriers at greater risk for sudden heart death.
The researchers made this discovery by sequencing the genes of 600 people who died from sudden cardiac death and 600 people of the same age who were healthy. Khera said they focused on 49 genes already known to be important for cardiovascular disease.
“These genes contribute to any of the four major causes [for sudden cardiac death],” he said. “Sometimes it’s a weak heart and the pumping function is not quite right. The second is a heart attack. The third is a problem with the heart’s rhythm. The last is a tear in a major blood vessel.”
After a geneticist on the team analyzed the genetic data, Khera said 14 different versions of 7 genes stood out.
“These 14 variants were found in 15 people. What’s really striking is that all 15 people were sudden cardiac death cases and zero were [healthy],” he explained.
The team reported their findings Saturday in the Journal of the American College of Cardiology.
After identifying the specific gene variants, the researchers looked at a larger database of 4,000 individuals. They found that about 1% of the population without a history of heart disease carries similar mutations in one of the 49 genes scientists believe are critical to heart health.
“It’s a really small percent of people, but an important percent," said Khera. "These people are predisposed to sudden cardiac death, and if we can find them then we have tools to prevent disease onset.”
Carrying one of those mutations doesn’t mean a person is certain to suffer from sudden cardiac death, Khera says. But his analysis suggests they do make the event three times more likely over a period of 15 years.
In most cases, doctors say sudden cardiac death arises from preventable causes.
“Most of the gene variations underlying [sudden cardiac death] are related to the electrical rhythm of the heart going chaotic or haywire," said Dr. Eric Topol, vice president of Scripps Research and a cardiologist who did not work on the study.
"There are many ways you can prevent this occurrence if you know a person has a high risk mutation,” Topol said. “Medications or a device like a defibrillator or pacemaker can fix the underlying problem.”
There are likely many more mutations that increase the risk for sudden cardiac death.
“The more we find of these, the more confident we are that they are the real deal, the better we will, in the future, be at preventing these catastrophes,” Topol said. “So, I think this is really important work.”
And not every sudden cardiac death strikes healthy individuals with no previous history of heart disease, Khera added.
“Of course, important lifestyle factors play a role, like smoking over the course of a lifetime or not well controlled blood pressure,” he said.
But often, families and friends of those who die from sudden cardiac death don’t get a reason for why it happened.
“The DNA can provide an explanation as to why this happened,” Khera said. “And even more importantly, this person’s family members may also have the gene variant, and if they know about it then they can take preventative measures.”
Editor's note: There are many mutations in the 49 genes researchers looked at in this study that may increase the risk of sudden cardiac death. Those "disease-causing" mutations occur in roughly 1% of the population, according to the research. The study focused on 14 of them.
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