What is the primary difference between atrial fibrillation and atrial flutter regarding heart rate?

The primary distinction in heart rate between atrial fibrillation and atrial flutter is that atrial fibrillation presents as irregularly irregular, while atrial flutter can exhibit a more organized rhythm that can be either regular or irregular.

In atrial fibrillation, the electrical signals in the atria are chaotic, leading to a disorganized contraction of the atrial muscles. This results in a heart rate that varies widely with no predictable pattern, termed "irregularly irregular." The randomness of the atrial contractions contributes to the varying intervals between ventricular beats, which can range significantly.

Conversely, atrial flutter is characterized by a more organized electrical circuit within the atrium, often resulting in a regular rhythm. While atrial flutter can be irregular at times, it typically manifests with a consistent pattern, such as a typical "sawtooth" pattern on an electrocardiogram (ECG) known as "f waves." This pattern may lead to a heart rate that is either consistently fast and regular or may occasionally have irregularities depending on the presence of conduction block or the ventricular response.

Understanding this difference is crucial for clinicians in diagnosing and determining the appropriate management strategies for patients with these arrhythmias.