Definition: A very rapid and abnormal heart rhythm (arrhythmia) caused by irregular electrical signals in the upper chambers (the atria) of the heart. The result is a disorganized, uncoordinated rhythm between heartbeat and pulse rate that can sometimes be felt as palpitations.
In some thyroid patients, hyperthyroidism -- and overactive thyroid -- can be a cause of atrial fibrillation.
Also Known As: auricular fibrillation, atrial fib, a-fib
