Rhythm Nation February 2015 – Answer

by eabram • March 8, 2015 • 3 Comments

Kudos go to Dr. Bryan Jarrett for an excellent interpretation!

Much discussion was had over this ECG.

There is an AV dissociation where the P waves march out.
There is a slightly wide QRS, but not that wide.

There is a small variability in the morphology of the QRS complexes.

All of these factors taken together lead to one of several options:

AV dissociation with accelerated junctional rhythm
1. Rare, unlikely as this patient was not on digoxin but not impossible
Ventricular tachycardia with AV dissociation
1. Idiopathic ventricular tachycardia difficult to diagnose
2. Fascicular VT (narrow QRS 100-140 msec)
  1. Posterior fascicular 90-95% of the time, RBBB morphology with left axis deviation
  2. Anterior fascicular 5-10%, LBBB morphology with right axis deviation or inferior deviation
3. Isorhythmic AV dissociation
  1. Another rare form of AV dissociation – sinus P waves and narrow QRS complexes where one beat is conducted and the next beat is an accelerated junctional beat at the same pace had the sinus beat been conducted
4. Yet another rhythm?

Of these rhythms, several will respond to adenosine and Fascicular VT will often respond to verapamil. Our ECG has predominantly left bundle branch morphology and an inferior axis which may lend itself to anterior fascicular block and less likely accelerated junctional rhythm.

Remember our patient had this fast “AVNRT” rhythm (seen below) that “broke” into our rhythm in question after adenosine:

So while the best answer now is some form of VT with AV dissociation, possible anterior fascicular VT, further EP studies are needed to definitively diagnose this rhythm. Further discussion is welcome!

References:
Lifeinthefastlane.com articles on: RVOT, Accelerated Junctional Rhythm and Fascicular Tachycardia

Enyon, CA et al. Fascicular Tachycardia: uncommon or just unrecognized? Emerg Med J 2002;19:477-478

Francis J, et al. Idiopathic Fascicular Ventricular Tachycardia. Indian Pacing Electrophysiol J. 2004 Jul-Sep; 4(3): 98–103.

Mattu A, Brady W. ECGs for the Emergency Physician 2, BMJ Books 2008

The views expressed on this blog are the author's own and do not reflect the views of their employer. Please read our full disclaimer here. Any references to clinical cases refer to patients treated at a virtual hospital, Janus General Hospital.