Distinguishing Ventricular Tachycardia (VT) from Supraventricular Tachycardia with aberrancy (SVT-A) is a critical skill in cardiology. When faced with a Regular Wide Complex Tachycardia (WCT), the three important diagnostic algorithms are Brugada, Vereckei, and Pava.
1. The Brugada Algorithm
The Brugada criteria is a four-step sequential “decision tree.” If any step is positive, you stop and diagnose VT. If none are met, the diagnosis is SVT.
| Step | Question | If YES… | If NO… |
| 1 | Absence of an RS complex in all precordial leads (V1–V6)? | VT | Move to Step 2 |
| 2 | Is the RS interval > 100 ms in any precordial lead? | VT | Move to Step 3 |
| 3 | Is there AV Dissociation (P waves independent of QRS)? | VT | Move to Step 4 |
| 4 | Are morphology criteria for VT present in V1-V2 and V6? | VT | SVT |
- Note on Step 2: The RS interval is measured from the start of the R-wave to the deepest part (nadir) of the S-wave.
- Note on Step 4: Look for “rabbit ears” in V1 where the left ear (R) is taller than the right (R’), or a QS complex in V6.
2. The Vereckei Algorithm (aVR Lead)
Vereckei simplified the process by focusing primarily on Lead aVR. Because aVR is essentially “looking down” from the right shoulder into the heart, VT (which often travels “up” from the apex) looks very different from SVT.
- Initial R wave: Is there an initial R wave in aVR? If yes -> VT.
- Initial r or q width: Is the width of the initial r or q wave > 40 ms? If yes -> VT.
- Notching: Is there notching on the initial downstroke of a predominantly negative QRS? If yes -> VT.
- Ventricular Activation Velocity Ratio (Vi/Vt): Compare the voltage change in the first 40 ms (Vi) to the last 40 ms (Vt). If Vi/Vt ≤ 1 (slow initial entry) -> VT.
3. The Pava Criterion (Lead II)
Pava et al. introduced an “ultra-simple” method focusing on Lead II. It is based on the principle that VT originates in the muscle (slow conduction) while SVT uses the specialized conduction system (fast initial conduction).
- Criterion: Measure the R-wave Peak Time (RWPT) in Lead II.
- Measurement: From the very beginning of the QRS complex to the first peak (or nadir, if negative).
- Threshold: If the RWPT ≥ 50 ms, the diagnosis is VT.