ECG Case 047

Middle-aged patient presenting with palpitations. Describe the ECG


Describe and interpret this ECG


This is another example of ventricular tachycardia, this time with a dominant S wave in V1/V2 and therefore a LBBB morphology (compare this with ECG 046).

Regular broad complex tachycardia at ~ 160 bpm.

Features of VT in V1:

  • Initial R wave > 30 ms wide, RS interval > 70 ms (Brugada sign)
  • Notching/slurring of the downslope of the S wave in V1/V2 (Josephson sign).

 Features of VT in V6:

  • Dominant S wave in V6; qR wave; absence of typical LBBB morphology
  • Abnormal axis with positive aVR, although does not quite meet criteria for northwest axis.

NB. Note that a positive Brugada sign only requires an RS interval of >60 ms when LBBB morphology is present, compared to >100 ms when RBBB morphology is present.

Brugada-criteria-LBBB-VT-V1-2 Wellens
Image reproduced from Wellens (2001). See references for link.

Dominant S Wave in V1 or V2 (LBBB Morphology)

Lead V1 or V2

ECG VT V2 S wave notch Josephson sign 700

Lead V6

ECG VT V6 qR wave LBBB morphology 700

These features are very different to the expected pattern in LBBB, which has:

  • Dominant S wave in V1, but with an R/S interval < 70 ms and minimal initial R wave.
  • Dominant R wave in V6 (often slurred).


Tips for Spotting VT when LBBB morphology present

[NB. LBBB morphology = QRS > 120ms with dominant S wave in V1]

Suspect VT in any patient with a regular broad complex tachycardia (esp if > 160 ms wide).

Look at aVR
  • Positive QRS complex?
  • Leads I and aVF negative?
  • If yes to both -> northwest axis is present -> probable VT.
Look at V1
  • Initial R wave > 30 ms? –> probable VT.
  • Notching of the S wave (Josephson’s sign)? –> probable VT.
  • RS interval > 70 ms (Brugada’s sign)? –> probable VT.
  • None of the above –> possible SVT with LBBB.
Look at V6
  • Dominant S wave (R/S ratio < 1)? -> probable VT.
  • Dominant R wave (R/S ratio > 1)?-> possible SVT with LBBB.

If still uncertain, scrutinise the ECG for:

If still uncertain…review the ECG for:
ECG VT AV dissociation

AV dissociation: superimposed P waves at a different rate to the QRS complexes

ECG VT Fusion beat capture beat

The first of the narrower complexes is a fusion beat, the next two are capture beats.


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

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