Scientists at DeCode Genetics Inc., of Reykjavik, Iceland, reported the discovery of single-letter variants in the sequence of the gene MYH6 associated with high risk of sick sinus syndrome in Icelanders. The study, published in the online edition of Nature Genetics, showed the lifetime risk of being diagnosed with the syndrome is about 6 percent for individuals without the genetic variant but is nearly 50 percent for those who carry it. Sick sinus syndrome is a heart rhythm disorder characterized by an inappropriately slow heart rate.