Is this VT?
Is this VT?
ER SURVIVAL GUIDE/Is this VT?

Is this VT?

Sub Title
Guide to differentiate VT from SVT using ECG analysis.
System
Circulation
Published
Dec 5, 2025
Good posts start with good questions. Have an ER question? Send it here.
KEY
🔍- Deep Dive
📌- Clinical Application
🔸 - Weak Evidence
🔹 - Strong Evidence
📑 - Evidence summaries
✅ - Recommended treatment
⚠️ - Critical Information
It’s 2 AM in your ED. Your triage nurse hands you an ECG.
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
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 and 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 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 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)
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
Look specifically for:
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
Just ONE of these ends the discussion → It’s VT.

2️⃣ Lead I negative, aVF negative?

Extreme axis
→ its 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)
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
  • 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
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
Any ? → VT

5️⃣ Look at V1–V6

  • RSR' (left rabbit ear taller)
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
  • Absence of RS complexes across precordials
Both favor VT.

6️⃣ Look at aVR

Initial R wave → strongly suggests VT.
ECG image: LITFL ECG Library (litfl.com)
ECG image: LITFL ECG Library (litfl.com)
If ANY features suggest VT → treat as VT.
If NONE of the above are present → then, and only then, consider SVT with aberrancy.
notion image
notion image
⚠️
Bottom Line : If you’re not absolutely certain it’s SVT It’s VT.
⚠️
And whatever you do: No verapamil in undifferentiated WCT. Ever.

Want to Read More?

  1. Burns, Ed, and Robert Buttner. "VT versus SVT.”
  1. Salim Rezaie, "SVT With Aberrancy Versus VT", REBEL EM blog, November 22, 2013.
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Disclaimer : For educational use only — always follow your clinical judgment and local protocols.