Brugada Criteria

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Introduction

In 1991 the Brugada Criteria[1] were published in Circulation. The criteria were established because the conventional criteria used to differentiate a Wide Complex Tachycardia lacked specificity. The Brugada criteria consisted of four criteria established by the authors, which were prospectively analyzed in a total of 554 tachycardias with a widened QRS complex (384 ventricular and 170 supraventricular). The sensitivity of the four consecutive steps was 0.987, and the specificity was 0.965.

Four Brugada Criteria for Diagnosis of Ventricular Tachycardia

  1. Lack of an RS complex in the precordial leads
  2. Whether the longest interval in any precordial lead from the beginning of the R wave to the deepest part of the S wave when an RS complex is present is greater than 100 ms
  3. Whether atrioventricular dissociation is present
  4. Whether both leads V1 and V6 fulfilled classic criteria for ventricular tachycardia.

Step 1: Lack of RS Complex

An RS complex was present in at least one precordial lead in all SVTs with aberrant conduction so this finding is 100% specific for the diagnosis of ventricular tachycardia. However, only 26% of VTs did not have an RS complex in any precordial lead. In other words if you do not see an RS complex it is VT, but if you see an RS complex you need to go to Step 2 because RS complexes are seen in both SVTs and some Ventricular Tachycardias.

Step 2: Whether the R to S interval in any precordial lead is greater than 100 ms

This is measured from the beginning of the R wave to the deepest portion of the S wave. An RS interval greater than 100 msec was not observed in any SVT with aberrant conduction. Half of the VTs which did have an RS complex in at least one precordial lead had an RS interval less than 100 msec and the other half of the VTs had an RS interval of greater than 100 msec. Thus, an RS interval of more than 100 msec in any precordial lead when an RS complex was present (Step 2) were each 100% specific for the diagnosis of VT.
How to measure RS complex
How to measure RS complex

Step 3: AV Dissociation

When looking at an EKG of a wide complex tachycardia it is always nice to see AV dissociation because it is 100% specific for the diagnosis of VT.

Step 4: Morphology Criteria

This step is the hardest to memorize and it is better to keep a reference card or just visit this website if you need to read over the criteria. If you do not make the diagnosis of VT with Steps 1-3 then the morphology criteria are analyzed in leads V1 and V6. If both leads have a morphology compatible with the diagnosis of VT, the diagnosis of VT is made. Otherwise, the diagnosis of SVT with aberrant conduction is made by exclusion.

Tachycardia with a right bundle branch block-like QRS

Lead V1

Monophasic R or QR or RS favors VT
Triphasic RSR' favors SVT

Lead V6

R to S ratio <1 (R wave smaller than S wave) favors VT
QS or QR favors VT
Monophasic R favors VT
Triphasic favors SVT
R to S ratio >1 (R wave larger than S wave)favors SVT

Tachycardia with a left bundle branch block-like QRS

Lead V1 or V2

Any of following R >30 msec, >60 msec to nadir S, notched S favors VT

Lead V6

Presence of any Q wave, QR or QS favors VT
The absence of a Q wave in lead V6 favors SVT

References

  1. A New Approach to the Differential Diagnosis of a Regular Tachycardia With a Wide QRS Complex. Pedro Brugada, MD; Josep Brugada, MD; Lluis Mont, MD; Joep Smeets, MD; and Erik W. Andries, MD. Circulation 1991;83:1649-1659
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