An arrhythmia is an irregular heart rhythm. An arrhythmia can occur with a normal heart rate or with fast or slow heart rates. Causes may include coronary artery disease, heart attack, heart surgery, blood imbalances, and more. There are many types of arrhythmias including atrial fibrillation and atrial flutter. Treatments include medications and lifestyle changes, cardioversion, pacemakers, ICDs, and surgery. Follow the links below to find WebMD's comprehensive coverage about how arrhythmia is caused, what it looks like, how to treat it, and much more.