The heart is a muscle about the size of your fist that pumps blood around the body. When the heart is functioning properly, it has a specific rhythm controlled by a mass of specialized heart tissue ...

An arrhythmia is a problem with your heartbeat’s rhythm and/or rate. Some arrhythmias are nothing to worry about, others should be monitored, and some need to be addressed immediately. The heart has ...

An arrhythmia is an irregular heartbeat. An arrhythmia may feel like a racing heart or fluttering. It is not always serious but can sometimes indicate a potentially fatal heart problem. Arrhythmias — ...

Medically reviewed by Jeffrey S. Lander, MD Key Takeaways Go to the hospital if a rapid heart rate is with chest pain, ...