12 Lead ECGs:
Injury/Infarct Imposters
Injury/Infarct Imposters
Conditions that make the identification of
acute injury/infarction DIFFICULT or
IMPOSSIBLE
Some Common Examples (not all inclusive
list)
Ventricular & Paced Rhythms
LBBB
LVH
Benign Early Repolarization
Pericarditis
Injury/Infarct Imposters
Imposters can incorrectly place an
ECG into any of the three categories
ST Elevation ST Depression Normal
BBB T wave inversion Non-diagnostic
Ventricular & Paced Rhythms
Can mask or mimic every ECG
change suggestive of ischemia/injury
Paced rhythms
Idioventricular rhythms
AIVR
V-Tach
PVCs
Ventricular & Paced Rhythms
Differential Diagnosis of Wide
Complex Tachycardias
Necessary for appropriate treatment
CCBs can be very bad in WPW
Identify factors that favor one rhythm
Possibilities:
VT, SVT with aberrant conduction,
Afib/Aflutter with aberrant conduction
Differential Diagnosis of Wide
Complex Tachycardias
Top 10 List for WCT*
1. Ventricular 6. VT
Tachycardia 7. VT
2. Ventricular Tach 8. VT
3. V Tach 9. SVT with preexisting BBB
4. VT 10. SVT with aberrant
5. VT conduction
* Ken Grauer. A Practical Guide to ECG Interpretation. 2nd Ed.
Differential Diagnosis of Wide
Complex Tachycardias
Factors Favoring VT
Concordance across all V leads (+/-)
ERAD axis deviation (“no man’s land”)
QRS > .14 sec
AV dissociation
Suggestive QRS morphology
Differential Diagnosis of Wide
Complex Tachycardias
Differential Diagnosis of Wide
Complex Tachycardias
Left Ventricular Hypertrophy
Enlarged left ventricle
Pumping against increased resistance
Chronic overfilling
LVH
May Produce May Hide
ST elevation ST elevation
ST depression ST depression
Tall T waves Tall T waves
Inverted T waves Inverted T waves
LVH
Does not abnormally widen QRS
Increases height and depth of
QRS
Recognized by this increase
Three step recognition formula
LVH
LVH Recognition
Step 1
Look in V1 and V2
Pick the deepest negative deflection (S
wave)
Count small boxes of negative deflection in
that lead
Remember that number
LVH Recognition
LVH Recognition
Step 2
Look in V5 and V6
Pick the tallest positive deflection (R
wave)
Count small boxes of positive
deflection
Remember that number
LVH Recognition
LVH Recognition
Step 3
Add the two numbers together
Suspect LVH if the sum is > 35 (> 35 mm)
LVH Recognition
LVH Recognition
Benign Early Repolarization
Benign Early Repolarization
Normal variant; Difficult to identify
Produces
ST elevation
Tall T waves
Changes usually seen in anterior & lateral
leads
Most often seen in males ages 20-40
More common in African-American males
Thin, young persons
Benign Early Repolarization
• Look for notch at J-point
– ST segment and J-point create a “fish hook”
appearance
Benign Early Repolarization
Pericarditis
Pericarditis
May be viral, bacterial or metabolic
Secondary to recent cardiac surgery
Post MI
IV Drug abuse
Clinical presentation may include CP
Often produces diffuse ST elevation on
ECG plus clinical presentation
Pericarditis
Correlate Diffuse ST segment elevation
with Clinical Presentation
Sharp, “Stabbing” chest pain
Can be localized
May be aggravated by movement or
inspiration. Patient may seek relief by sitting
upright, leaning forward
May radiate to back, base of neck, between
shoulder blades, left shoulder or arm
Pericarditis
May produce ST elevation in any lead
May be in all leads
May not be anatomically grouped
J-point notching often present
Fish hook or ‘Smiley Face’
PR segment depression
Very specific for pericarditis
Other ECG findings
Low voltage
Electrical alternans
Pericarditis
Medications
Some medications affect the ECG
Digitalis
Shortened QT interval
ST depression
Characteristic sag
Medications: Digitalis Effect
Digitalis Effect
Summary
Imitators can produce ST elevation or
depression
Imitators can eliminate ST elevation
or depression
Most frequent imitators
LVH
BBB
Paced rhythms
Summary
If QRS is wide
Consider BBB
Consider ventricular rhythm (or paced)
If QRS is narrow
Consider LVH
Consider pericarditis
Consider early repolarization
Summary
“Fish hooks” often seen with:
Pericarditis
BER
“Fish hooks” can also be seen with
ACS
Summary
The presence of a potential imposter
DOES NOT ALWAYS
make it impossible to identify injury/infarction