A racing or fluttering heart can be a sign of an arrhythmia — a problem with the rate or rhythm of your heartbeat. One of the most common types is atrial fibrillation, also called AFib. With AFib, the heart beats irregularly and sometimes much faster than normal. The upper and lower chambers of the heart do not work together as they should. This can cause symptoms like dizziness, fatigue, and a pounding heartbeat. AFib is most often caused by changes in the heart's tissue or its electrical signals. Conditions like high blood pressure, coronary artery disease, infections, and aging can trigger these changes. AFib may come and go in brief episodes, or it can become a lasting condition. Treatment is important because AFib can raise your risk for stroke and other heart problems. Talk to your care team if your heart races or flutters.