At least 3 million to 6 million people have atrial fibrillation, also known as AFib. It’s one of the most common types of arrhythmia, or irregular heart rhythm. And experts estimate the condition will ...

Atrial fibrillation happens most often in older adults and in people with other heart problems. But it also affects younger people. Roughly 800,000 Americans under age 40 have atrial fibrillation, ...