Answer: With a special app.
The app could be used to detect an irregular heartbeat known as atrial fibrillation that can cause blood clots, a stroke or even heart failure. Normally, atrial fibrillation is hard to detect without the use of an electrocardiogram.
Led by researcher Tero Koivisto, a research team at the University of Turku, Finland, has created an app that can detect atrial fibrillation with 96 percent accuracy. The research was based on a discovery in 2011 by the university and Turku University Hospital that small accelerometers can accurately detect atrial fibrillation by monitoring chest movements. Since most smartphones contain accelerometers, all they had to do was develop an app that could analyze the data from the accelerometer when the user placed the device on their chest.
Circulation Journal has published a paper on the team’s research.