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EKG Challenge – November 2018

Resident Author: Evan Kuhl
Resident Editor: Jennifer Rabjohns
Faculty Mentor: Massoud Kazzi
Date of Presentation: 11/29/2018

65yoM p/w palpitations for 2 days.

How would you describe this EKG?
The EKG above shows a regular, narrow complex tachycardia.

What is the differential diagnosis?
A narrow complex tachycardia is supraventricular, meaning it originates above the ventricles before the His-Purkinje system.

If this was an irregular rhythm, then atrial fibrillation, variable flutter, or multifocal atrial tachycardia would be more likely.

Regular supraventricular tachycardias (SVT) include sinus tachycardia, atrial flutter, AV nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT)1.

NEJM has a good review2 of these, and this is their ddx algorithm:

AVNRT is more common, is typically rapid in onset, with regular palpitations. Generally, AVNRT is well tolerated without hemodynamic instability. AVNRT occurs when there are two pathways through the AV node, a slow and fast conducting pathway. Normal sinus rhythm is conducted through the fast pathway, however if a stimuli arrives to the AV node while the fast pathway is still in a refractory state, the slow pathway is activated, which may lead to the reentry phenomena.

AVRT is less common, occurs when a reentry circuit is present in an accessory pathway outside the AV node, and may have several different EKG morphologies3. Wolff-Parkinson-White is an example of one AVRT.

Schematics are from the same NEJM review article2:

On closer examination of this EKG, you can also see retrograde P-waves (blue arrows, below).

This EKG is a case of AVNRT.

How would you treat this patient?

If this patient became unstable, you would immediately cardiovert the patient using the synchronized cardioversion setting. Since he was stable, modified vagal maneuvers were attempted without success4. A single dose of 6mg of adenosine was then used to chemically terminate the arrhythmia. A second dose of 12mg adenosine could be attempted if the first dose fails.

Our illustrious resident on the case recorded the continuous EKG showing the cardioversion.


  1. Tintinalli JE, Stapczynski JS, Ma OJ, Cline D, Meckler GD, Yealy DM. Chapter 18, Tintinalli's emergency medicine : a comprehensive study guide: New York : McGraw-Hill Education, 2016. Eighth edition.; 2016.
  2. Link, M. Evaluation and Initial Treatment of Supraventricular Tachycardia. NEJM;367:1438-1448. DOI: 10.1056/NEJMcp1111259.
  3. Supraventricular Tachycardia - Life in the Fast Lane ECG Library. @sandnsurf, 2018. at
  4. Appelboam A, Reuben A, Mann C, et al. Postural modification to the standard Valsalva manoeuvre for emergency treatment of supraventricular tachycardias (REVERT): a randomised controlled trial. Lancet 2015;386:1747-53.

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