The Apple Heart Study, a collaboration between Apple and Stanford (and partnership with American Well and BioTelemetry), uses data from Apple Watch to identify irregular heart rhythms, including those from potentially serious heart conditions such as atrial fibrillation.

Atrial fibrillation (also called AFib or AF) is a quivering or irregular heartbeat (arrhythmia) that can lead to blood clots, stroke, heart failure and other heart-related complications. According to the American Heart Association, if you have AFib, you’re five times more likely to have a stroke than someone who doesn’t. If your heart beats too fast, it may even lead to heart failure. AFib can cause blood to clot in your heart. Blood clots can travel in the bloodstream, eventually causing a blockage (ischemia).

News media coverage:

Dec 11, 2017: Why This FDA Approval Could Be a Huge Deal for Apple (The Motley Fool)
Dec 4, 2017: Apple’s First Medical Study Signals Broader Health Ambitions (WSJ)
Nov 30, 2017: Apple Heart Study launches to identify irregular heart rhythms (Apple Newsroom)
Nov 30, 2017: Apple and Stanford begin Heart Study to detect irregular heart rhythms using Watch (9to5Mac)
Nov 30, 2017: Stanford begins irregular heartbeat research using Apple Watch data (Endgadget)
Nov 30, 2017: Apple Watch will alert heart-study participants if they have an irregular beat (USAToday)