TABLE OF CONTENTS
It’s 2 AM in your ED. Your triage nurse hands you an ECG.
And the dreaded question pops up
“Is this VT or SVT with aberrancy?”
Let’s start with a mindset shift, Don’t ask “Is this VT or SVT?”
Ask instead:
“Is there anything here that absolutely PROVES it’s not VT?”
Because if the answer is no, then it IS VT until proven otherwise. That is what we are going to try to achieve in this post.
And remember:
No algorithm can safely rule out VT.
Err on the side of VT.
Always.
Step 1 — Is the Patient Stable?
Use ACLS algorithm - CHAAS
- Chest pain?
- Hypotension?
- Altered Mental Status?
- Acute heart failure?
- Signs of shock?
👉 If ANY are present: do not waste time dissecting the ECG.
ALL unstable WCTs = VT.
Step 2 — Take a quick history
Now that you know your patient is stable, talk to them and ask a quick history
Ask these four questions:
- Age > 35 years?
- Prior MI?
- Known structural heart disease?
- Family history of sudden cardiac death?
👉 If any are positive → VT is far more likely.
Step 3 — Look for Old ECGs
- Previous SVT reverted with adenosine
- WPW on earlier ECGs
- Chronic BBB pattern
👉 Any positive → SVT becomes more likely.
Step 4 — Check the Rate
Come back to your patient and look at the monitor
<120 / min = Think Mimics
- Hyperkalemia
- Sodium-channel blocker toxicity
- AIVR (accelerated idioventricular rhythm)
Step 5 — Now Dissect the ECG
Now you can look at the ECG again
1️⃣ Can you see a P before every QRS?
If not → VT
AV Dissociation (The Money Shot)
Look specifically for:
Just ONE of these ends the discussion → It’s VT.
2️⃣ Lead I negative, aVF negative?
Extreme axis
→ it's VT
3️⃣ QRS Duration?
>160 ms (≥4 small boxes) → VT
>200 ms (≥5 boxes) →
- Hyperkalemia
- Sodium-channel blocker overdose
4️⃣ Bundle Branch Pattern?
Dominant S in V1/V2?
It looks like LBBB
Check for:
- V1
- R wave > 30 ms
- RS interval >100 ms (Brugada sign)
- Notched S wave (Josephson sign)
- V6
- QS or qR
Any ? → VT
Dominant R in V1/V2
It looks like RBBB
Check for:
- V1
- Smooth, monophasic R
- Notched downslope
- qR pattern
- V6
- QS
- R/S ratio <1
Any ? → VT
5️⃣ Look at V1–V6
- RSR' (left rabbit ear taller)
- Absence of RS complexes across precordials
Both favor VT.
6️⃣ Look at aVR
Initial R wave → strongly suggests VT.
If ANY features suggest VT → treat as VT.
If NONE of the above are present → then, and only then, consider SVT with aberrancy.
Bottom Line: If you’re not certain it’s SVT, it’s VT.
And whatever you do: No verapamil in undifferentiated WCT. Ever.
Want to Read More?
- Burns, Ed, and Robert Buttner. "VT versus SVT.”
- Salim Rezaie, "SVT With Aberrancy Versus VT", REBEL EM blog, November 22, 2013.
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