From the Guidelines
Atrial flutter on ECG appears as a characteristic "sawtooth" pattern of atrial activity, with regular, rapid atrial waves (F waves) occurring at a rate of 240-300 bpm, producing predominantly negative F waves in ECG leads II, III, and aVF, and a positive deflection in V1. This distinct ECG pattern reflects a macroreentrant circuit, most commonly in the right atrium, and helps differentiate atrial flutter from other supraventricular arrhythmias like atrial fibrillation or sinus tachycardia 1. The atrial rate can be slower in some patients due to conduction delays in the atrial circuit, and the circuit can also rotate in the opposite direction, resulting in positive F waves in the inferior ECG leads and negative in V1 1. Key characteristics of atrial flutter on ECG include:
- Regular, rapid atrial waves (F waves) at a rate of 240-300 bpm
- Predominantly negative F waves in ECG leads II, III, and aVF
- Positive deflection in V1
- Variable AV block, leading to 2:1, 3:1, 4:1, or irregular conduction patterns
- Normal QRS complexes unless there is concurrent bundle branch block or aberrant conduction. Unusual flutter wave morphologies can occur in the presence of substantial atrial disease, prior surgery, or radiofrequency catheter ablation 1.
From the Research
ECG Appearance of Atrial Flutter
The electrocardiogram (ECG) appearance of atrial flutter is characterized by:
- A "sawtooth" pattern of flutter waves with negative polarity in leads II, III, and aVF, as described in 2
- A typical flutter rate ranging between 240-250 beats/min, as mentioned in 3
- Sawtooth-like flutter waves that start negative in II, III, and aVF and then show a steep slope upwards to the isoelectric line, as highlighted in 3
Variations in ECG Appearance
There are variations in the ECG appearance of atrial flutter, including:
- Positive or biphasic flutter waves in right atrial flutter in a clockwise rotation, flutter around the vena cava inferior or superior, and around a scar, as described in 3
- Positive flutter waves in V1 for left atrial flutter waves, as mentioned in 3
- Heterogeneous flutter wave morphology in left atrial flutter, as noted in 3
Classification of Atrial Flutter
Atrial flutter can be classified based on electrophysiologic mechanisms and anatomic bases, as proposed in 4, which includes:
- Focal tachycardias characterized by radial spread of activation and endocardial activation not covering the whole cycle
- Macroreentrant tachycardias characterized by circular patterns of activation that cover the whole cycle
- Atrial flutter as a mere description of continuous undulation on the ECG, with only some strictly defined typical flutter patterns correlating with right atrial macroreentry, as mentioned in 4