BASE HOSPITAL GROUP ONTARIO Chapter 10 for 12 Lead Training -12 Lead Interpretation – Part 2- Ontario Base Hospital Group Education Subcommittee 2008 TIME IS MUSCLE
Chapter 10 - 12 lead Interpretation - Part 2
Jul 15, 2015
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BASE HOSPITAL GROUPONTARIO
Chapter 10 for 12 Lead Training
-12 Lead Interpretation – Part 2-
Ontario Base Hospital GroupEducation Subcommittee
2008
TIME IS MUSCLE
OBHG Education Subcommittee
12 Lead Interpretation – Part 2
REVIEWERS/CONTRIBUTORS
Neil Freckleton, AEMCA, ACPHamilton Base Hospital
Jim Scott, AEMCA, PCPSault Area Hospital
Ed Ouston, AEMCA, ACPOttawa Base Hospital
Laura McCleary, AEMCA, ACPSOCPC
Tim Dodd, AEMCA, ACPHamilton Base Hospital
Dr. Rick Verbeek, Medical DirectorSOCPC2008 Ontario Base Hospital Group
AUTHOR
Greg Soto, BEd, BA, ACPNiagara Base Hospital
OBHG Education Subcommittee
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 AMIExplain the reasons why a normal ECG
does not rule out AMI
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Epicardial Coronary Artery
Lateral Wall of LV
Positive Electrode
Septum
Left Ventricular
Cavity
Inferior Wall of LV
Ischemia
Thrombus forming
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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 WaveHyperacute T Wave
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Evolution of AMI
• AcuteAcute
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Evolution of AMI
• AcuteAcute
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Evolution of AMI
• Age undeterminedAge 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 BERLVH
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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 AMINot all AMI have STE (approx. 50%)Early AMI may have no STE but may
evolve over timeNon 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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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.
Why can’t AMI be ruled out?
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Practice
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Practice
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Practice
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QRS
Q wavesPhysiologic 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/seriousnessseverity/seriousness
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Sample ECGs with Q-waves
Find them……….
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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
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Reciprocal Changes
Occur in larger MIAble to “see” the MI on the opposite side
because it is larger
RC’s make the STE more likely to be due to AMIDon’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, aVFII, III, aVF I, aVL, V leadsI, aVL, V leads
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Reciprocal Changes
Inferior
Anterior = Septal, Anterior and Lateral walls
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Practice
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Practice
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AMI Recognition
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AMI Recognition
Imitators of infarctBBB LVHVentricular beatsPericarditisEarly RepolarizationOthers
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Summary
AMI recognitionKnow what you are looking for
> 1mm of ST elevation in limb leads> 2mm of ST elevation in chest
leadsTwo contiguous leads
Know where you are lookingPositive electrode as an “eye”Memorize lead locations
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Summary
Reciprocal ChangesNot necessary to presume
infarctionStrong 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
BASE HOSPITAL GROUPONTARIO
QUESTIONS?
BASE HOSPITAL GROUPONTARIO
Well Done!
Education Subcommittee
START QUIT
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