Both the Josephson Sign and the Brugada Sign are specific morphological “clues” on an ECG that help confirm a diagnosis of Ventricular Tachycardia (VT) rather than Supraventricular Tachycardia (SVT) with aberrancy.
While the Brugada Criteria is a full 4-step algorithm, the Brugada Sign refers to one specific measurement within that algorithm.
Josephson Sign
The Josephson Sign is a finding related to the “slowness” and fragmentation of ventricular activation when an impulse originates in the muscle itself rather than the normal conduction system.
- What it looks like: A notching or “saw-tooth” slurring near the nadir (the very bottom) of the S-wave.
- Where to find it: Usually seen in the precordial leads (V1–V6) or lead III.
- Significance: It is highly specific for VT. It represents delayed activation of the ventricular myocardium, often due to the impulse traveling around scar tissue (re-entry).
Brugada Sign
In the context of differentiating VT from SVT, the Brugada Sign refers to a specific timing interval.
Note: Do not confuse this with “Brugada Syndrome,” which is a genetic condition involving ST-elevation in V1-V2.
- What it looks like: The interval from the onset of the R-wave to the nadir of the S-wave is > 100 milliseconds (2.5 small boxes).
- Significance: In normal conduction, ventricular activation is usually fast because it uses the Purkinje fibers. In VT, the initial depolarization is slow because it moves cell-to-cell through the muscle, “stretching” this interval.
Reference
- Brugada P, Brugada J, Mont L, Smeets J, Andries EW. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation. 1991 May;83(5):1649-59. doi: 10.1161/01.cir.83.5.1649. PMID: 2022022.
Why these matter
When you are looking at a Wide Complex Tachycardia (WCT), the default is to treat it as VT. However, these signs give you the confidence to confirm it:
- If you see a notch (Josephson sign), the muscle is likely activated abnormally.
- If the downslope takes too long (Brugada sign, not syndrome), the impulse didn’t start in the normal “high-speed” conduction system.