Rhythm Nation

Rhythm Nation November 2014 Answer!

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Excellent answer by Dr. Kylie Birnbaum!

This patient indeed has a supraventricular tachycardia (SVT), and indeed was found to have fast-slow atrioventricular nodal re-entrant tachycardia (AVNRT) on later electrophysiologic study. In the ED at Janus General, however, vagal maneuvers failed and 6mg of Adenosine was ordered. Just prior to administration this patient self-converted back to normal sinus rhythm with a heart rate of 86.

As Dr. Birnbaum mentioned, AVNRT is the most common form of paroxysmal SVT, and is more common in women than men by a 3:1 ratio. Rate can be widely variable between 140 and 280 bpm, and have sudden onset or regression. AVNRT has a functional accessory pathway and is differentiated from atrioventricular re-entrant tachycardia (AVRT) which has an anatomic pathway.

AVNRT has a more common (80-90%) slow (anterograde)  and fast (retrograde) conduction which usually has P waves buried within the QRS complex. Less commonly, AVNRT will have fast (anterograde) and slow (retrograde) conduction with a P wave after the QRS such as with our patient. Very uncommon is slow-slow conduction.

Differential for an atrioventricular origin can also include an accelerated junctional rhythm (AJR, 60-100 bpm) or junctional tachycardia (JR, >100 bpm), but these are uncommon. AJR is classically associated with digoxin toxicity.

Differential for an atrial origin with regular rhythms include sinus tachycardia, atrial tachycardia, atrial flutter and sinus node re-entrant tachycardia. Irregular rhythms from the atria include multifocal atrial tachycardia, atrial flutter with variable conduction block and atrial fibrillation.

Treatment of AVNRT: adenosine, then calcium-channel blockers or beta-blockers. If the patient is unstable, cardioversion may be required.

References:

Issa, Z et al. Clinical Arrhythmology and Electrophysiology: A Companion to Braunwald’s Heart Disease, Chapter 17 (Atrioventricular Nodal Reentrant Tachycardia), 381-410.

Life in the Fast Lane: SVT

In conjunction with Dr. Jennifer Martindale.

 

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.
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1 comment for “Rhythm Nation November 2014 Answer!”

  1. Ian deSouza
    November 26, 2014 at 10:50 am

    Nice job Birnbaum and Abram. Here are some more good reviews:

    Am Fam Physician. 2010 Oct 15;82(8):942-52.
    Common types of supraventricular tachycardia: diagnosis and management. Colucci RA, Silver MJ, Shubrook J. PMID: 20949888

    N Engl J Med. 2006 Mar 9;354(10):1039-51.
    Clinical practice. Supraventricular tachycardia.
    Delacrétaz E. PMID: 16525141

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