23-29: Atrial Flutter

ECG Findings

• Regular narrow-complex tachycardia.

• Flutter waves appear in a rapid sine wave or “sawtooth” pattern, usually in the inferior leads (II, III, aVF).

• Atrial activity in lead V₁ often appears as rapid P waves at a rate approximating 300 bpm.

Pearls

1. The AV node’s refractory period usually prevents 1:1 conduction to the ventricles. Usually, conduction is blocked at a ratio of 1:2 to 1:4. The QRS complexes should appear with regular periodicity. However, AV conduction may be variable from beat to beat, creating irregular R-to-R intervals.

2. A conduction ratio of 2:1 is usually difficult to discern, because the two flutter peaks between QRS complexes may look like normal P and T waves. A ventricular rate of 140 to 160 bpm should prompt consideration of the possibility of atrial flutter with 2:1 block.

3. Atrial flutter tends to be more refractory to chemical cardioversion and more susceptible to electrical cardioversion when compared to atrial fibrillation.