Researchers have found nine new gene variations that can make a person vulnerable to sudden cardiac death and confirmed the role of another, international researchers said on Sunday.

"Almost half were surprising new genes that no one would have guessed as being involved in cardiac biology," said Dan Arking of Johns Hopkins University School of Medicine, whose team was one of many working on the study in the journal Nature Genetics.

Last month, Arking's group reported in the journal Circulation that it had found a single gene that raises the risk of cardiac death. The new study identifies that gene plus nine new ones that modify the timing of heart contractions, a measure known as the QT interval.

People with prolonged QT intervals have a higher risk of cardiac death, which accounts for more than 400,000 deaths each year in the United States, according to the American College of Cardiology.

"Sudden cardiac death is a real problem. You don't get a second chance," Arking said in a telephone interview.

Click here to watch a video about Sudden Cardiac Arrest.

The study of 15,842 people showed that the more of these 10 variants a person has, the greater the chances of having a prolonged QT interval.

A heart attack can raise the risk of having this type of abnormal heart rhythm, but people who inherit this genetic risk are often never identified.

"The problem in some sense is most of these people have no known risk factors. They don't have high cholesterol. They are not obese. In some sense, the genetics may be the only hope for some of these people," Arking said.

The next step is to try to identify how great a role each of these genes play in raising risks. Ultimately, he said, the findings might offer a target for new drugs.