Working with ECGs
Dr Cynthia Lim
Dr Dean Pritchard
FACEMs, Emergency Department
The Northern Hospital
ECG 123s
– Measurement of electrical flow across the heart
using electrodes placed on the chest and limbs
– Deviation of electrical flow from normal pathways
indicates cardiac anomaly or cardiac disease
The Leads
• Limb Leads
– aVR – Right arm
– aVL – Left arm
– aVF – Left leg
• Vectors
–
–
–
–
Flow of +ve current
I – R arm  L arm
II – R arm  L leg
III – L arm  L leg
The Leads
• Chest leads
–
–
–
–
–
–
V1
V2
V3
V4
V5
V6
Axis
Look at leads I
and avF
If in left quadrant
then look at lead II
Successive approximation method
ECG Morphology
Pick the Problem…
NORMAL ECG
ECG of 2 year old – normal or abnormal?
Higher rate, Partial RBBB pattern, Dominant R V1, R axis deviation
Chest Pain
The Barn Door…
Acute anterior ST elevation myocardial infarction
The Barn door
Acute inferior ST elevation myocardial infarction
What about this?
Septolateral Non-ST Elevation Myocardial Infarction
And this?
Acute Pericarditis
ACS – STEMI
• Any ST dep except V1 or aVR (allowed in acute
pericarditis)
• ST elevation III > II
• Horizontal or convex up ST elevation
• New Q waves
ACS – acute pericarditis
• PR dep multiple leads
– Only reliably seen viral
– transient
• Low voltage and tachycardia = large
pericardial effusion
• Friction rub
• Use T-P as baseline (not P-P interval)
• If in doubt serial ECGs
T-wave Changes
• T-wave inversions
– STEMI – After the
appearance of ST
changes
– NSTEMI – After a period
of hyperacute T-wave
changes
• May persist for months
or permanently