Scientists combing the human genome have discovered ten common genetic mutations that boost the risk of sudden cardiac arrest by subtly disrupting the heart beat, two studies released on Sunday reported.
The findings shed light on the cause of the irregular rhythms that often underlie severe heart problems, and could point to new treatments, said the study, published in Nature Genetics.
Heart disease is the number one killer worldwide, claiming upward of 17 million lives every year, according to the World Health Organization.
Smoking, obesity and high cholesterol are common risk factors, but genes can be a critical factor too.
In the absence of symptoms, identifying genetic variants that affect the timing of heart contractions - known as the "QT interval" - could become a critical means of predicting the likelihood of sudden cardiac death.
An international team of more than 40 scientists, led by Arne Pfeufer of Munich University, analysed the genomes of nearly 16,000 individuals whose QT intervals had been measured by electrocardiogram.
They screened some 2.5 million sites on each genome, trying to match subtle alterations in gene sequence with aberrant patterns of heart contractions.
The study turned up ten bits of wayward genetic code. One, a gene known as Nos1ap, had already been identified as contributing to heart trouble, and several others had been placed on a list of suspects.
"But almost half were surprising new genes that no one would have guessed as being involved in cardiac biology," said Dan Arking, a professor at John Hopkins University in Baltimore, and a co-author of the study.
"So it really does open up a new world of investigation because these are genes that would have never come up if we had only focused on a list of known candidates."
In separate research, scientists led by Christopher Newton-Cheh at Massachusetts General Hospital found similar results from more than 13,000 individuals.
"We were very reassured to see such strong replication in two independent studies," he said in a press statement.
A single genetic variation in an individual does not necessarily mean a higher risk of an irregular heart beat, much less increased risk of sudden cardiac death, the researchers pointed out.
But when all the data is taken together, the results become statistically significant.
"The reason people die from this cardiovascular disorder is because we know nothing about the antecedents," said Aravinda Chakravarti, also a professor at John Hopkins and a co-author of the first study.