Transcript Slide 1
ONTARIO
BASE HOSPITAL GROUP
Chapter 10
for 12 Lead Training
-12 Lead Interpretation – Part 2Ontario Base Hospital Group
Education Subcommittee
2008
TIME IS
MUSCLE
12 Lead Interpretation – Part 2
AUTHOR
REVIEWERS/CONTRIBUTORS
Greg Soto, BEd, BA, ACP
Neil Freckleton, AEMCA, ACP
Hamilton Base Hospital
Niagara Base Hospital
Jim Scott, AEMCA, PCP
Sault Area Hospital
Ed Ouston, AEMCA, ACP
Ottawa Base Hospital
Laura McCleary, AEMCA, ACP
SOCPC
Tim Dodd, AEMCA, ACP
Hamilton Base Hospital
2008 Ontario Base Hospital Group
Dr. Rick Verbeek, Medical Director
SOCPC
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Chapter 10 - Objectives
Recognize
ST-depression and relate to the
ACS patient
Recognize Reciprocal Changes (RCs) and
relate to the significance of STEMI
Recognized Q-waves and relate to the ACS
patient
Discuss the evolution of an AMI
Explain the reasons why a normal ECG
does not rule out AMI
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Ischemia
Epicardial Coronary Artery
Septum
Thrombus forming
Left
Ventricular
Cavity
Lateral Wall of LV
Positive Electrode
Inferior Wall of LV
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Ischemia
Inadequate
oxygen to tissue
Subendocardial
Represented by ST depression or
T-wave inversion
May or may not result in infarct
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ST depression
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T-wave Inversion
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Evolution of AMI
• Hyperacute T Wave
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Evolution of AMI
• Acute
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Evolution of AMI
• Acute
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Evolution of AMI
• Age undetermined
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Hyper-acute T-waves
Earliest
ECG sign of
AMI
Tall and peaked w/in
minutes of blood flow
interruption
Differential Dx:
hyperkalemia
BER
LVH
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Why hyper-acute T-wave are
important to recognize
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AMI Recognition
A “normal” 12-lead ECG
DOES NOT rule out AMI
Not
all AMI have STE (approx. 50%)
Early AMI may have no STE but may
evolve over time
Non STEMI AMI have non specific but
abnormal ECGs
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Why can’t AMI be ruled out?
PHECG has high specificity for STEMI = 97%*
Meaning = when PHECG shows STEMI it
almost always turns out to be an AMI.
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Why can’t AMI be ruled out?
PHECG has only moderate sensitivity for AMI =
68%
Meaning - when PHECG does not show STEMI
only 68% of time does it turn out to NOT be an
AMI. (over 30% of AMI patients do not have STE
on PHECG)
CAN’T RULE OUT AMI WITH NO STE
on 12 LEAD ECG
Source: Ioannides JA et al. Accuracy & clinical effect of out-of-hospital ECG
in the diagnosis of acute cardiac ischemia: a meta-analysis. Annals of
Emergency Medicine 2001;37.
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Practice
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Practice
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Practice
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QRS
Q
waves
Physiologic Q waves
< .04 sec (40ms)
Pathologic Q waves
>.04 sec (40 ms)
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Q-wave & Infarct
represent
irreversible necrosis – death
of tissue
may develop early (1st hour) but
usually 8-12 hours post-AMI
may persist permanently but some
resolve regardless of reperfusion
not all AMIs produce Q-waves
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QRS
Q
wave
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QS Complex
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Common Q-waves
“age
undetermined”
Likely old septal MI
↑ index of suspicion not
a bad idea
Q-wave
associated with
an AMI = necrosis has
likely begun
↑ severity/seriousness
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Sample ECGs with
Q-waves
Find them……….
Septal – V1 to V3
(? – II, III, aVF )
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Lateral - aVL
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aVL, V1 – V5
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Reciprocal Changes
Reciprocal Changes
Occur
in larger MI
Able to “see” the MI on the opposite side
because it is larger
RC’s
make the STE more likely to be
due to AMI
Don’t have to have RC’s but they make
the diagnosis easier
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Reciprocal Changes
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Reciprocal Changes
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Reciprocal Changes
II, III, aVF
I, aVL, V leads
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Reciprocal Changes
Anterior =
Septal,
Anterior and
Lateral walls
Inferior
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Practice
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Practice
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AMI Recognition
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AMI Recognition
Imitators
of infarct
BBB
LVH
Ventricular
beats
Pericarditis
Early
Repolarization
Others
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Summary
AMI recognition
Know what you are looking for
> 1mm of ST elevation in limb leads
> 2mm of ST elevation in chest
leads
Two contiguous leads
Know where you are looking
Positive electrode as an “eye”
Memorize lead locations
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Summary
Reciprocal
Changes
Not
necessary to presume
infarction
Strong confirming evidence
when present
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Summary
ST
segment elevation is
presumptive evidence
for AMI
Other
conditions may
also cause ST elevation
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Summary
NEVER FORGET:
A normal 12-Lead ECG DOES
NOT rule out AMI
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BASE HOSPITAL GROUP
QUESTIONS?
ONTARIO
BASE HOSPITAL GROUP
Well Done!
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