The atria are the upper chambers of the heart. Atrial fibrillation is uncontrolled electrical activity in the atria that causes the atrial walls to quiver rather than contract normally. All but which of the following are true statements about atrial fibrillation?
Electrocardiography (ECG) confirms the diagnosis.
The heart beats very slowly.
The heart beats irregularly.
Atrial fibrillation is more common among older people.
