Mar 19 • Paramedic Talk
The Spatial Anatomy of a 12-Lead ECG
Great short video to explain 12 lead anatomy.
A STEMI occurs when a coronary artery is occluded, causing ischemia in the area that artery supplies.
👉 The leads showing ST elevation = the area of the heart that is injured👉 That area corresponds to a specific coronary artery
Coronary Artery Overview
There are two main coronary arteries:
1. Left Main Coronary Artery (LMCA)
Splits into:
- Left Anterior Descending (LAD)
- Left Circumflex (LCx)
2. Right Coronary Artery (RCA)
Gives off:
- Right Marginal Artery
- Posterior Descending Artery (PDA) (in most people)
Left Anterior Descending (LAD)
What it Supplies
- Anterior wall of left ventricle
- Septum
- Often the apex of the heart
ECG Findings (Anterior STEMI)
ST elevation in:
- V1
- V2
- V3
- V4
Key Concept
LAD occlusion = anterior MI
⚠️ This is the most dangerous STEMI (“widow maker”) because it affects a large portion of the heart.
Left Circumflex (LCx)
What it Supplies
- Lateral wall of the left ventricle
ECG Findings (Lateral STEMI)
ST elevation in:
- I
- aVL
- V5
- V6
Key Concept
LCx occlusion = lateral MI
Right Coronary Artery (RCA)
What it Supplies
- Right ventricle
- Inferior wall of left ventricle
- Often the SA node and AV node
ECG Findings (Inferior STEMI)
ST elevation in:
- II
- III
- aVF
Key Concept
RCA occlusion = inferior MI
⚠️ May cause:
- Bradycardia
- Hypotension
Posterior Descending Artery (PDA)
Origin
- Usually from the RCA (right-dominant circulation)
What it Supplies
- Posterior wall of the left ventricle
- Posterior septum
ECG Findings (Posterior MI)
Posterior MIs are not directly seen on standard 12-lead.
Instead you see:
ST depression in:
- V1
- V2
- V3
👉 This is a mirror image of posterior ST elevation
Confirmation Leads
- V7
- V8
- V9 → show ST elevation
Right Marginal Artery
What it Supplies
- Right ventricle
ECG Relevance
- No unique lead pattern
- Can contribute to right ventricular infarction
Right Ventricular MI Clue
Occurs with proximal RCA occlusion
Look for:
- Inferior STEMI + hypotension
- Confirm with V4R
8:18
1
0 comments
The Spatial Anatomy of a 12-Lead ECG
skool.com/rescueacademy
Calling ALL future EMTs & Paramedics. Let's PASS the National Registry on the FIRST attempt.
Leaderboard (30-day)
1
+9
2
+6
3
+5
4
+4
5
+4
Powered by