Atrial flutter is a type of supraventricular tachycardia which arises secondary to re-entry circuit in the right atrium. Following features may be demonstrated on ECG in case of atrial flutter: - Narrow QRS-complex tachycardia - Atrial activity > 300 bpm - Loss of isoelectric baseline - Upright flutter waves in V1 may mimic P waves - Saw-tooth pattern in lead II, III, and avF Reference: https://litfl.com/atrial-flutter-ecg-library/ Image via: https://litfl.com/wp-content/uploads/2018/08/Atrial-flutter-with-a-3-1-block.jpg