What is Arrhythmia? Atrial fibrillation (AFib), is a common form of arrhythmia. The condition occurs when there are erratic electrical signals between the upper chambers of the heart, or atria. These signals confuse the heart’s natural rhythm, causing the atria to squeeze too quickly. As a result, the heart fibrillates, or quivers. Learn More About AFib Request an Arrhythmia Appointment Schedule Now