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Supraventricular Tachycardia (SVT) With Aberrancy Versus Ventricular Tachycardia (VT)


2011_04_22AwmEPRDifferentiating between SVT with aberrancy and VT can be very difficult. It is crucial to be able to make this distinction as therapeutic decisions are anchored to this differentiation. Brugada et al prospectively analyzed 384 patients with VT and 170 patients with SVT with aberrant conduction to see if it was possible to come up with a simple criteria to help differentiate between the two with high sensitivity and specificity.

The Brugada criteria algorithm involves 4 sequential questions. If at any point, the answer is YES, then it is VT. 1

1. Is there an absence of an RS complex in all precordial leads?

    • Yes = VT (Sensitivity 0.21, specificity 1.0)
    • No = Next question
Screen Shot 2013-07-18 at 10.50.45 PM

Various forms of RS complexes are circled

2. Is the R to S interval >100 msec (2.5 small boxes) in one precordial lead?

  • Yes = VT (Sensitivity 0.66, specificity 0.98)
  • No = Next question

3. Is there atrioventricular (AV) dissociation?

  • Yes = VT (Sensitivity 0.82, specificity 0.98)
  • No = Next Question


  • AV Dissociation = Ventricular rate is same or faster than the atrial rate
  • Complete Heart Block = Atria are beating independent of ventricles with atrial rate being faster than ventricular rate

4. Is there morphology criteria for VT present in precordial leads V1/V2 and V6?

  • Yes = VT (Sensitivity 0.987, specificity 0.965)
  • No = SVT with Aberrant Conduction (Sensitivity 0.965, specificity 0.987)
  • Determine if you have a LBBB morphology (dominant S wave in V1) or a RBBB morphology (dominant R wave in V1) then use the appropriate section below to help differentiate.

4a. LBBB Morphology: Dominant S Wave in V1 or V2

  • Lead V1 morphology consistent with VT:
    • R wave > 30 msec (PPV 0.96)
    • RS interval > 60 msec (PPV 0.96), as measured from R wave onset to S wave nadir
    • Notched S Wave (Josephson’s Sign)
Lead V1

Lead V1

  • Lead V6 morphology consistent with VT:
    • QS complex (PPV 1.0)
    • qR wave (PPV 1.0)
Lead V6

Lead V6

4b. RBBB Morphology: Dominant R Wave in V1 or V2

  • Lead V1 morphology consistent with VT:
    • Smooth, monophasic R wave (PPV 0.78)
    • Notched downslope to R wave (PPV 0.90)
    • qR wave (PPV 0.95)
Lead V1

Lead V1

  • Lead V6 morphology consistent with VT:
    • QS complex (PPV 1.0)
    • R/S Ratio < 1 (PPV 0.87)
Lead V6

Lead V6

Following the above stepwise approach can help differentiate between SVT with aberrancy and VT with very good sensitivity and specificity.

Brugada P, Brugada J, Mont L, Smeets J, Andries E. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation. 1991;83(5):1649-1659. [PubMed]

Expert Peer Review

Validations of the Brugada method have not had very good results.

Here is one that had, for Emergency physician #1, a sensitivity of 83% (95% CI = 78% to 91%) and a specificity of 43% (95% CI = 25% to 59%), while EP #2 attained 79% (95% CI = 73% to 87%) and 70% (95% CI = 51% to 84%) :

Verekei has subsequently published 2 criteria which are much easier to apply and performed better than the Brugada criteria:

This one, which is still a bit complex:

AND a second one which uses aVR only:

I have a post on differentiating VT and SVT with aberrancy using the Sasaki rule, which has not been validated either, but is even simpler than either Vereckei rule.  I use it as a final step if I don’t have the diagnosis from 6 earlier steps.  Of course, the diagnosis is not nearly as important as the management, which is easily accomplished by electrical cardioversion.

Stephen W. Smith, MD
Faculty Emergency Physician, Hennepin county Medical Center, Associate Professor, University of Minnesota
Salim Rezaie, MD

Salim Rezaie, MD

ALiEM Associate Editor
Clinical Assistant Professor of EM and IM
University of Texas Health Science Center at San Antonio
Founder, Editor, Author of R.E.B.E.L. EM and REBEL Reviews
  • Christopher

    Brugada’s approach to VT/SVT is alright, but the work of Vereckei and Sasaki has shown you can definitely improve upon the sensitivity and specificity by including aVR into your criteria.

    The honest answer is to really capture the gamut of VT vs SVT cases, you need to be familiar more than one criteria and have a sound understanding of how these findings play into your Rx. Sometimes regardless of the rhythm, the safest answer is sedation and synchronized cardioversion.

    • Salim R. Rezaie


      Thank you for your comments. I agree multiple criteria are important to know, and some of the other criteria which you mentioned are also good. The Verecki aVR criteria which you mention (Link: ) is also good. Just as with anything else in medicine, no one criteria is absolute. Both are a nice systematic way to help differentiate VT from SVT with aberrancy. I think the important thing is to realize there are multiple criteria, none are perfect, and be sure to know where to find them in those crucial times you need to make therapeutic decisions. Thank you again for taking the time to read the post.


    • Michelle

      There are quite a few different algorithms none have been shown to be more accurate than the classic Brugada, but there are different SN and SP numbers. Agreed that we should know different rules.

      • Christopher

        I think that paper reflects the accuracy of the decision tools moderately well, but I did not feel that it reflects their utility in actual practice.

        Their comments on Figure 1 illustrate this discrepancy when they claim that aVR has a Q-wave. They continue with the note that the aVR algorithm would only accept this as VT because it has a bad Vi/Vt ratio which, “required a magnifying glass”. I won’t discount the ridiculous effort involved in the Vi/Vt ratio calculation (Sasaki improved on this), but I certainly wonder how they mistook AV dissociation for a Q-wave.

        From a practical standpoint their statements on the LR’s is especially relevant:

        “The ‘yes’ or ‘no’ algorithm approach to VT/SVT diagnosis does not provide information regarding the strength of the reached diagnosis. Using LRs do provide such information, which can be helpful to the clinician. Indeed, if several algorithm results are concordant, it is theoretically possible to multiply the LRs of those algorithms to further strengthen the final diagnosis.”

  • Stephen Smith

    I hate to say this, but In real EM, it barely matters whether you can make this differentiation or not. Just use electricity. That said, readers may be interested in this post of mine:

    • Ronny

      It matters! SVT = Adenocor iv over 2 sec!

      • Ronny

        And now i read your blog. Good job there!