ANN ARBOR—You’re sitting at your desk and suddenly your heart is beating in overdrive or worse, lurching along like a car on fumes. It is a shocking, uncomfortable and frightening sensation.

Irregular heart rhythms are a common cause of sudden cardiac death or SCD, a condition that accounts for 450,000 deaths annually in the United States. Scientists are now closer to understanding what causes SCD and who it may strike, said Gon