12-Lead 12-Lead ElectrocardiographyElectrocardiography

a comprehensive course

Adam Thompson, EMT-P, A.S.Adam Thompson, EMT-P, A.S.

STE-Mimics

Part 1

The 6-Step MethodThe 6-Step Method

• 1. Rate & Rhythm1. Rate & Rhythm

• 2. Axis Determination2. Axis Determination

• 3. Intervals3. Intervals

• 4. Morphology4. Morphology

• 5. STE-Mimics5. STE-Mimics

• 6. Ischemia, Injury, & Infarct6. Ischemia, Injury, & Infarct

What is a STEMI?

• STEMI = ST-Elevated Myocardial Infarction

• Its how we “diagnose” someone with an MI in the field and activate a “STEMI Alert”

ST-Segment

STE-Mimics LessonsSTE-Mimics Lessons

• STE-MimicsSTE-Mimics– Any cause of ST-Elevation or AMI-like Any cause of ST-Elevation or AMI-like

patterns that is not associated with an patterns that is not associated with an actual MI.actual MI.

ObjectivesObjectives

• Learn what the different STE-Mimics are.Learn what the different STE-Mimics are.• Learn how to identify a STE-Mimic.Learn how to identify a STE-Mimic.• Learn how to differentiate between a STE-Learn how to differentiate between a STE-

Mimic and a STEMI Mimic and a STEMI – (ST-Segment Elevation Myocardial Infarction)(ST-Segment Elevation Myocardial Infarction)

ST-ElevationST-Elevation

• The most common cause of ST-The most common cause of ST-elevation is not myocardial infarction. elevation is not myocardial infarction.

• Less than 50% of STEMI alerts called Less than 50% of STEMI alerts called by paramedics are actually ACS by paramedics are actually ACS patientspatients

ST-ElevationST-Elevation

• ST-Elevation is elevation of the J-Point which ST-Elevation is elevation of the J-Point which causes elevation of the following ST-causes elevation of the following ST-Segment.Segment.

• Elevation is defined as anything above the Elevation is defined as anything above the isoelectric line.isoelectric line.

• Find the isoelectric line by locating the TP-Find the isoelectric line by locating the TP-Segment.Segment.

T P

TP-Segment

ST-ElevationST-Elevation

• The J-Point is where the QRS complex The J-Point is where the QRS complex and the ST-Segment meet.and the ST-Segment meet.J-Point

Causes of ST-ElevationCauses of ST-Elevation

Listed from most common to least:Listed from most common to least:• Left ventricular hypertrophy (LVH) Left ventricular hypertrophy (LVH) • Left bundle branch block (LBBB)Left bundle branch block (LBBB)• Benign early repolarization (BER) Benign early repolarization (BER) • Right bundle branch block (RBBB)Right bundle branch block (RBBB)• Nonspecific BBBNonspecific BBB• Ventricular AneurysmVentricular Aneurysm• PericarditisPericarditis• Undefined or unknown causeUndefined or unknown cause

Causes of ST-ElevationCauses of ST-Elevation

Easier way to remember:Easier way to remember:E - Electrolytes (hyperkalemia)E - Electrolytes (hyperkalemia)

L - LBBBL - LBBB

E - Early repolarizationE - Early repolarization

V - Ventricular hypertrophy (LVH)V - Ventricular hypertrophy (LVH)

A - AneurysmA - Aneurysm

T - Treatment (e.i. pericardiocentesis)T - Treatment (e.i. pericardiocentesis)

I - Injury (AMI, contusion)I - Injury (AMI, contusion)

O - Osborne waves (hypothermia)O - Osborne waves (hypothermia)

N - Non-occlusive vasospasmN - Non-occlusive vasospasm

Lead PlacementLead Placement

• Poor ECG captures Poor ECG captures were noted as a were noted as a common problem.common problem.

• V3 is most commonly V3 is most commonly misplaced leadmisplaced lead

What are Contiguous Leads?What are Contiguous Leads?

• Contiguous leads are leads that look at Contiguous leads are leads that look at the same area of the heart. the same area of the heart.

• They show up on the 12-lead proximal They show up on the 12-lead proximal to each other.to each other.

Lead I

high lateral

aVR V1

septal

V4

anterior

Lead II

inferior

aVL

high lateral

V2

septal

V5

low lateral

Lead III

inferior

aVF

inferior

V3

anterior

V6

low lateral

Reciprocal ChangesReciprocal Changes

• Reciprocal changes are changes like Reciprocal changes are changes like ST-depression or T-Wave inversion in ST-depression or T-Wave inversion in leads opposite to the site of injury.leads opposite to the site of injury.

Site Facing ReciprocalSeptal V1, V2 None

Anterior V3, V4 None

Lateral I, aVL, V5, V6 II, III, aVF

Inferior II, III, aVF I, aVL

Posterior V7, V8, V9 V1, V2, V3, V4

Left Ventricular HypertrophyLeft Ventricular Hypertrophy

• The The ““Strain PatternStrain Pattern”” is a repolarization is a repolarization abnormality associated with LVH and abnormality associated with LVH and may cause ST-Segment changes.may cause ST-Segment changes.

• STEMI is more difficult, but still possible STEMI is more difficult, but still possible to identify in the presence of LVH.to identify in the presence of LVH.

LV Strain PatternLV Strain PatternLeft Precordial Leads Right Precordial LeadsLeft Precordial Leads Right Precordial Leads

V4, V5, V6 V1, V2, V3V4, V5, V6 V1, V2, V3

Normal Complex

LV StrainLV Strain

• Discordance means opposite.Discordance means opposite.– T-Wave discordance means that the T-T-Wave discordance means that the T-

Wave is deflected in the opposite direction Wave is deflected in the opposite direction as the terminal (last) wave of the QRS.as the terminal (last) wave of the QRS.

– T-Wave discordance is normal in every T-Wave discordance is normal in every lead with Left or Right BBBs.lead with Left or Right BBBs.

LVH CluesLVH Clues

• T wave Discordance (widened QRS/T angle)T wave Discordance (widened QRS/T angle)• Concave ST-Segments with asymmetrical T Concave ST-Segments with asymmetrical T

waveswaves• The height of STE and T waves are directly The height of STE and T waves are directly

proportionate to the depth of the S waves.proportionate to the depth of the S waves.– The taller the R wave the deeper the ST The taller the R wave the deeper the ST

depression.depression.• STE in right precordial leads with depression in left STE in right precordial leads with depression in left

precordial leads due to precordial leads due to ““strain patternstrain pattern””. .

LV-StrainLV-Strain

LV-StrainLV-Strain

LV-StrainLV-Strain

LV-Strain

The EndThe End

• More in the next lessonMore in the next lesson