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Jason's Blog: ECG Challenge of the Week for August 19-26. The value of a previous, comparative ECG.

jer5150's picture

Patient clinical data:  68-year-old black man.

(1.)  What "pseudo" clue in Fig. 1 clinches the source of the mechanism seen in Fig. 2?

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A Pseudo-R' in V1 and Pseudo-S in II (although II already has a true S from LAFB) are suggestive of AVNRT, coupled with the PAC in first strip make that mechanism for the tachycardia seem more likely.

Christopher's picture

Christopher & VinceD are right on the mark. Jason soon coming with a gorgeous laddergram. I'd just add its always nice when you can see evidence of reentry (retrograde conduction back over the fast pathway producing notch in terminal part of the QRS) in many leads. In the 2nd tracing - in addition to leads V1 & lead II - we also see that retrograde P in leads III,aVR,aVF,V5 and V6 - which as per Vince "clinches" the diagnosis of reentrant SVT.

Ken Grauer, MD   [email protected] 

jer5150's picture
Submitted by jer5150 on

Interpretation:  (Fig. 1)
(1.)  Sinus rhythm (rate about 82/min) with . . .
(2.)  . . . so-called “first-degree” A-V block (P-R = 0.26s).
(3.)  Left axis deviation (LAD; about -59 degrees) probably due to . . .
(4.)  . . . left anterior hemiblock (LAHB). 
(5.)  One atrial premature beat (APB; 10th beat) with prolonged P’-R interval .
(6.)  One atrial “echo” (i.e., reversed reciprocal beat) producing “pseudo r’-wave” (oblique arrow).   

Interpretation:  (Fig. 2)
(1.)  Atrioventricular nodal reentrant tachycardia (AVNRT) at a rate of about 143/min.
(2.)  One probable ventricular fusion beat (F; 24th beat)
(3.)  Left axis deviation (LAD; about -66 degrees) probably due to . . .
(4.)  . . . left anterior hemiblock (LAHB).  

Many thanks to Christopher, Vince, and Ken for participating in this week’s case study.  There is very little left for me to contribute to their respective answers.   Both of these serial ECGs were recorded in separate, consecutive years.  In the laddergram's A-V tiers, the solid lines (i.e., ––––––––– ) represent conduction via the fast pathway (FP) and the broken / dashed lines (i.e., - - - - - - - - ) represent conduction via the slow pathway (SP).

Jason E. Roediger - Certified Cardiographic Technician (CCT)
[email protected]

The pseudo R prime in V-1 during the tachycardia that is not present before the tachycardia is not only suggestive

 of slow-fast AVNRT, it is diagnostic of it. In a large EP study, this was 100% diagnositic of slow-fast AVNRT.

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