MONDAY, Dec. 27 (HealthDay News) -- Scientists have identified DNA sequence variations associated with abnormal heart rhythms that can cause heart damage and sudden death.

The international team studied nearly 50,000 people worldwide and found variants in 22 locations across the human genome that can effect QRS interval -- a measure of electrical depolarization in the heart's lower chambers (ventricles).

QRS interval is easily measured on an electrocardiogram (EKG). A prolonged QRS interval has been associated with increased risk for heart problems and sudden cardiac death.

Among the significant findings were variations in two side-by-side genes that regulate electrically charged particles to produce signals that activate heart contractions. One of these genes, SCN5A, is known to play a role in controlling how signals start from specialized muscle cells and travel across the heart to cause rhythmic contractions. It had not been known that the neighboring gene, SCN10A, played any role in cardiac electrical activity at all.

"The size of this study really gave us the power to identify many genes not previously suspected to play a role in heart conduction," corresponding author Dan Arking, an assistant professor at McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, said in a Hopkins news release.

The study was published recently in Nature Genetics.

More information

The U.S. National Heart, Lung, and Blood Institute has more about heart rhythm problems.