- Narrow complex tachycardia
- Regular atrial activity at ~300 bpm
- Flutter waves (“saw-tooth” pattern) best seen in leads II, III, aVF — may be more easily spotted by turning the ECG upside down!
- Flutter waves in V1 may resemble P waves
- Loss of the isoelectric baseline
- Narrow complex tachycardia at 150 bpm (range 130-170)? Yes -> Suspect flutter!
Fixed AV blocks
- 2:1 block = 150 bpm
- 3:1 block = 100 bpm
- 4:1 block = 75 bpm