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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

Screen-Shot-2013-07-18-at-10.50.47-PM

3. Is there atrioventricular (AV) dissociation?

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

Screen-Shot-2013-07-19-at-1.09.54-AM1

    • 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)

Screen Shot 2013-07-23 at 2.48.47 AMLead V1 

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

Screen Shot 2013-07-23 at 2.48.57 AM

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)

Screen Shot 2013-07-23 at 3.05.25 AMLead V1

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

Screen Shot 2013-07-23 at 3.05.30 AMLead V6

 

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

 

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%) : 

http://onlinelibrary.wiley.com/doi/10.1111/j.1553-2712.2000.tb02267.x/abstract         

 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:

           http://eurheartj.oxfordjournals.org/content/28/5/589.full 

         AND a second one which uses aVR only:

           http://www.heartrhythmjournal.com/article/S1547-5271%2807%2900943-5/abstract.

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.

http://hqmeded-ecg.blogspot.com/2011/10/wide-complex-tachycardia-ventricular.html 

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

References

  1. P. Brugada, J. Brugada, L. Mont, J. Smeets, and E.W. Andries, "A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex.", Circulation, 1991. http://www.ncbi.nlm.nih.gov/pubmed/2022022
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