Characteristics of Atrial Flutter
Atrial flutter is a narrow-complex tachyarrhythmia with an atrial rate that can exceed 300/min, can develop in children with congenital heart disease, and is not typically seen in newborn infants with normal hearts. The rhythm does NOT have distinctly present P waves or regular atrioventricular conduction in the traditional sense.
Correct Characteristics:
Narrow-complex tachyarrhythmia ✓
Atrial flutter presents as a supraventricular tachycardia with narrow QRS complexes (assuming no underlying bundle branch block or aberrant conduction). The ventricular response depends on AV nodal conduction properties 1, 2.
Atrial rate that can exceed 300/min ✓
The atrial rate in typical atrial flutter ranges from 240 to 320 beats per minute in the untreated state 1, 2. The 2015 ACC/AHA/HRS guidelines specifically note that the atrial rate can be slower than the typical 300 bpm in the presence of antiarrhythmic drugs or scarring, but can also exceed this rate 3, 4. Type II flutter was historically designated for rates faster than 340 bpm 5.
Can develop in children with congenital heart disease ✓
While the guidelines focus primarily on adult populations, atrial flutter is well-recognized in pediatric patients with congenital heart disease, particularly those with surgical scars creating anatomical substrates for macroreentrant circuits 3, 4.
Not seen in newborn infants with normal hearts ✓
Atrial flutter in neonates is distinctly uncommon in structurally normal hearts and typically occurs in the setting of congenital heart disease or other structural abnormalities.
Incorrect Characteristics:
Regular atrioventricular conduction ✗
This is misleading. While atrial flutter itself shows regular atrial activation with a characteristic saw-tooth pattern, the AV conduction is typically variable. Most commonly, atrial flutter presents with 2:1 AV block, resulting in a ventricular rate of 120-160 bpm (characteristically about 150 bpm), but the AV conduction ratio can vary (3:1,4:1, or variable block), producing either regular OR irregular ventricular rates 1, 2, 6.
Distinctly present P wave ✗
This is fundamentally incorrect. Atrial flutter is characterized by flutter (F) waves, NOT discrete P waves. The guidelines explicitly state that flutter waves show a "saw-tooth pattern of regular atrial activation" that is "particularly visible in leads II, III, aVF, and V1" without an isoelectric baseline between deflections 1, 2. This distinguishes flutter from focal atrial tachycardia, which does have discrete P waves with isoelectric segments between them 5, 7.
Key Distinguishing Features:
- ECG Pattern: Continuous undulating baseline with saw-tooth flutter waves, no isoelectric baseline 1, 2
- Mechanism: Macroreentrant circuit, most commonly around the tricuspid annulus through the cavotricuspid isthmus 3, 4
- Typical morphology: Negative flutter waves in leads II, III, aVF; positive in V1 for counterclockwise (typical) flutter 1, 5