ECG Case 048

30-year old female presenting with sudden onset of palpitations. Normally well. Describe the ECG.

TOP 100 ECG QUIZ LITFL 048 2

Describe and interpret this ECG

ECG ANSWER and INTERPRETATION

On first glance this would appear to be SVT with LBBB as there is:

  • Regular broad-complex tachycardia.
  • No atrial activity seen.
  • Typical LBBB morphology in aVR, V1 and V6.
  • No obvious diagnostic features for VT — compare this with ECG 047.

However, there is one feature here that is unusual for LBBB, can you spot it?

Reveal answer

There is an rightward / inferior axis (around +90 degree)., which is atypical for Left Bundle branch block. LBBB normally has a leftward axis.

This combination of…

  • Broad complex tachycardia with typical LBBB morphology.
  • Inferior axis (+90 degrees).

… is suggestive of a specific type of VT known as right ventricular outflow-tract tachycardia (RVOT).

RVOT is a relatively common form of right ventricular VT, occurring in two main groups:

It may be very difficult to differentiate RVOT from SVT with LBBB.

[NB. Left bundle branch block morphology simply indicates that the heart is depolarising from right to left. Hence, similar QRS patterns are seen with LBBB, RVOT and RV-pacing]


CLINICAL PEARLS

Tips for Spotting RVOT

  • Suspect RVOT when you see LBBB morphology + inferior axis.
  • Record a long rhythm strip looking for fusion and capture beats.

I have diagnosed this only a couple of times in the past. Each time I had to stand by the monitor with my finger on the “print” button waiting for a fusion or capture beat to appear before anyone would believe me!


TOP 100 ECG SERIES


Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

One comment

  1. Very nice ECG. I believe there is also AV dissociation apparent upon closer inspection (best seen V1, V4 and the rhythm strip), which pushed me in the direction of VT. I thought that would be a nice addition in the line of the previous two cases.
    Thanks for these ECG’s. They are helping me in my 12 lead training.

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