Atrial fibrillation (A-fib) is an irregular and often very rapid heart rhythm (arrhythmia) that can lead to blood clots in the heart. A-fib increases the risk of stroke, heart failure and other heart-related complications. During atrial fibrillation, the heart’s upper chambers (the atria) beat chaotically and irregularly — out of sync with the lower chambers (the ventricles) […]