Smartphone-based tool helps detect irregular heartbeat in American Indians American Heart Association News FacebookTwitterEmail A smartphone-based screening tool can accurately detect previously undiagnosed atrial fibrillation, an irregular heart rhythm that puts people at high risk for stroke, according to new research that shows it could help uncover the condition in American Indians. The study, published Wednesday in the Journal of the American Heart Association, reported a smartphone-based electrocardiogram detected AFib in a group of American Indians, half of whom were younger than the recommended screening age of 65. The device was tested on American Indians because they are more at risk for AFib than people in other racial and ethnic groups.