Atrial Flutter vs SVT

Atrial flutter and SVT can both present as a regular narrow-complex tachycardia and can be hard to differentiate.

  • 2:1 atrial flutter is frequently mistaken for SVT because flutter waves may be hidden within T waves. Carefully inspect inferior leads and V1
  • Flutter often has atrial rates 250-350 bpm
  • SVT usually has rates 150-250 bpm

Key EKG Clues

Atrial Flutter vs SVT
Feature Atrial Flutter SVT
Typical ventricular rate ~150 bpm with 2:1 block 150-250 bpm
Rhythm Regular or variable Very regular
P waves Sawtooth flutter waves, although hard to see in 2:1 or 1:1 Often hidden or retrograde
Baseline No true isoelectric baseline Usually flat baseline
Best leads II, III, aVF, V1 P waves often difficult to see
Adenosine effect Reveals flutter waves Often terminates rhythm

When in doubt...

  • A regular narrow-complex tachycardia at ~150 bpm is atrial flutter until proven otherwise

Suggests Atrial Flutter

  • Rate persistently around 150 bpm
  • Sawtooth waves in inferior leads
  • Flutter waves visible in V1
  • Adenosine slows AV conduction but does not terminate rhythm

Suggests SVT

  • Sudden onset/termination
  • Extremely regular rhythm
  • No clear flutter waves
  • Adenosine terminates tachycardia

Best way to distinguish

  • Give adenosine to slow them down and look for flutter waves (if atrial flutter) versus termination entirely to NSR (if SVT)

References

  1. Page, R. L., Joglar, J. A., Caldwell, M. A., Calkins, H., Conti, J. B., Deal, B. J., Estes, N. A. M., III, Field, M. E., Goldberger, Z. D., Hammill, S. C., Indik, J. H., Lindsay, B. D., Olshansky, B., Russo, A. M., Shen, W.-K., Tracy, C. M., & Al-Khatib, S. M. (2016). 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Journal of the American College of Cardiology, 67(13), e27–e115. https://doi.org/10.1016/j.jacc.2015.08.856
  2. Katritsis, D. G., Boriani, G., Cosio, F. G., Hindricks, G., Jais, P., Josephson, M. E., Keegan, R., Kim, Y.-H., Knight, B. P., Kuck, K.-H., Lane, D. A., Lip, G. Y. H., Malmborg, H., Oral, H., Pappone, C., & Themistoclakis, S. (2020). 2019 ESC guidelines for the management of patients with supraventricular tachycardia. European Heart Journal, 41(5), 655–720. https://doi.org/10.1093/eurheartj/ehz467
  3. Cosío, F. G. (2017). Atrial flutter, typical and atypical: A review. Arrhythmia & Electrophysiology Review, 6(2), 55–62. https://doi.org/10.15420/aer.2017.5.2
  4. Gupta, A., Perera, T., Ganesan, A., Sullivan, T., Lau, D. H., Roberts-Thomson, K. C., & Sanders, P. (2021). Adenosine: A drug with myriad utility in the diagnosis and treatment of arrhythmias. Journal of Arrhythmia, 37(1), 103–112. https://doi.org/10.1002/joa3.12456
  5. Saoudi, N., Cosío, F., Waldo, A., Chen, S.-A., Iesaka, Y., Lesh, M., Saksena, S., Salerno, J., Schoels, W., & Working Group of Arrhythmias of the European Society of Cardiology. (2001). Classification of atrial flutter and regular atrial tachycardia according to electrophysiologic mechanism and anatomic bases: A statement from a joint expert group. European Heart Journal, 22(14), 1162–1182. https://doi.org/10.1053/euhj.2001.2658