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This post is an answer to the ECG Case 238

• Rate: ~145 bpm
• Rhythm:
  • Subtle irregularity in rate
    • Periods of fixed rate of 150 bpm in leads V1-3
    • Periods of rate change best seen in lead V6
  • No p waves seen

• Axis: LAD
• Intervals:
  • QRS – Prolonged (120-140ms)
  • QT – 400ms (QTc Bazette 380-400 ms)
• Segments:
  • Discordant ST segment / T wave changes
• Additional:
  • LBBB morphology
    • Sgarbossa negative
  • Subtle change in QRS morphology best seen in V4-6 as rate changes

Interpretation

Wide Complex Tachycardia with LBBB morphology and left axis deviation.

What are the differentials ?

• SVT – with either baseline LBBB, would need old ECG’s to compare, or aberrancy / rate related block.
  • Most likely mechanism is atrial tachycardia or atrial flutter with 2:1 block with slower variable block at start / end of rhythm strip.
• VT – bundle branch re-entry
• Antidromic AV re-entry tachycardia with atriofascicular pathway

READ MORE:

• Never Mistake Ventricular Tachycardia for Supraventricular Tachycardia with Aberrant Conduction
• Know the Mimics of Ventricular Tachycardia

SIMILAR CASE: Wide QRS Tachycardia – SVT or VT ?