What Is an Arrhythmia? An arrhythmia is an uneven heartbeat. It means your heart is out of its usual rhythm. It may feel like your heart skipped a beat, added a beat, or is "fluttering." It might feel like itβs beating too fast (which doctors call tachycardia) or too slow (called bradycardia). Or you might not notice anything. Arrhythmias can be an emergency, or they could be harmless. If you feel something unusual happening with your heartbeat, get medical help right away so doctors can find out why it's happening and what you need to do about it.πΉπΉπΉπΉ