ECG Case 046

Middle-aged patient presenting with palpitations. Describe the ECG


Describe and interpret this ECG


This ECG contains multiple diagnostic features for ventricular tachycardia:; dominant R wave in V1/V2 and therefore a RBBB morphology (compare this with ECG 047)

  • Regular broad complex tachycardia at ~150 bpm.
  • Very broad QRS complexes (~200 ms).
  • Northwest axis (-120 degrees) with positive QRS in aVR.
  • Time from onset of the QRS complex to nadir of the S-wave > 100ms in any of the precordial leads (Brugada 1991)
  • Notching/slurring of the downslope of the S wave in V1/V2 (Josephson’s sign 1988)

Northwest Axis

ECG VT Northwest Axis

Dominant R Wave in V1 or V2 – RBBB Morphology

Note the presence of morphology criteria favouring VT over RBBB such as Tall monophasic R wave in V1; Dominant S wave in V6

Lead V1 and V2 morphology

ECG VT V1 R wave RS interval RBBB morphology 700

ECG VT V2 RS interval RBBB morphology 700

Lead V6 morphology

ECG VT V6 R-S ratio RBBB morphology 500

This pattern in V1 and V6 is very different from the expected morphology in RBBB. RSR’ pattern in V1 and Dominant R wave with wide slurred S wave in V6

RSR’ pattern in V1 with RBBB
Dominant R wave with wide slurred S wave in V6
ECG RBBB William MORROW Morrow


Tips for Spotting VT when RBBB morphology present

[NB. RBBB morphology = QRS > 120ms with dominant R wave in V1]

Suspect VT in any patient with a regular broad complex tachycardia (especially 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
  • Monophasic R wave; qR wave; or taller left rabbit ear? -> probable VT.
  • RSR’ pattern with taller right rabbit ear? -> possible SVT with RBBB.
Look at V6
  • Dominant S wave (R/S ratio < 1)? -> probable VT.
  • Dominant R wave with wide slurred S wave -> possible SVT with RBBB.
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.

For more tips on spotting VT, read this article.


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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