12 lead-lesson 5
TRANSCRIPT
12-Lead 12-Lead ElectrocardiographyElectrocardiography
a comprehensive course
Adam Thompson, EMT-P, A.S.Adam Thompson, EMT-P, A.S.
Lesson
5
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. 6. Ischemia, Injury, & InfarctIschemia, Injury, & Infarct
Lesson FiveLesson Five
• STEMISTEMI– ST-Segment Elevated Myocardial InfarctionST-Segment Elevated Myocardial Infarction– ST-Segment Elevation of > 1mm in two contiguous ST-Segment Elevation of > 1mm in two contiguous
leads. leads. – In V2 & V3, ST-Segment elevation must be at least In V2 & V3, ST-Segment elevation must be at least
2mm.2mm.
*The smaller the QRS complex, the more significant minimal ST-*The smaller the QRS complex, the more significant minimal ST-
Elevation is.Elevation is.
Objectives
• Learn how to identify a STEMI
• Learn how to localize the infarcted area
• Apply everything learned thus far
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
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
Coronary Circulation
Left Main
Circumflex(LCx)
Left Anterior Descending(LAD)
Right Coronary Artery(RCA)
Coronary Circulation
Right Coronary Artery
(RCA)
Left Circumflex Artery
(LCx)
Left Anterior Descending
(LAD)
•Right Atrium•Inferior Wall•Inferior-Right Ventricle
•Posterior Wall - 85% of population
•Inferior Wall•Isolated Right Ventricle
•Posterior Wall - 15% of population
•Anterolateral•Inferolateral•Posterolateral
•Anterior•Anteroseptal•Anteroseptal-lateral
*Nicknamed “Widow-maker”
Coronary Occlusion
Heart Anatomy
Lateral Wall
Septal
Inferior
Anterior
Heart Anatomy
Epicardium
Endocardium
Myocardium
Ischemia, Injury, Infarct
ST-Elevation
• The most common cause of ST-elevation is not myocardial infarction.
• Less than 50% of STEMI alerts called by paramedics are actually Acute Coronary Syndrome (ACS) patients
ST-Elevation
• ST-Elevation is elevation of the J-Point which causes elevation of the following ST-Segment.
• Elevation is defined as anything above the isoelectric line.
• Find the isoelectric line by locating the TP-Segment.
T P
TP-Segment
ST-Elevation
• The J-Point is where the QRS complex and the ST-Segment meet.J-Point
ST-Segment Morphology
Concave Convex
J-Point J-Point
Evolution of MI
• Insufficient blood supply to the myocardium.– Ischemia, injury or infarction, or all three.
• The branches of coronary arteries arising from the aortic root are distributed on the epicardial surface of the heart.
• These in turn provide intramural branches that supply the cardiac muscle.
• Myocardial ischemia generally appears first.
Evolution of MI
InfarctionIschemia
Injury
Needs O2 Damage from Irreversible lack of O2 damage
Ischemia
• Subendocardial ischemia– Ischemia in this area prolongs local recovery time.
Since repolarization normally proceeds in an epicardial-to-endocardial direction, delayed recovery in the subendocardial region due to ischemia does not reverse the direction of repolarization but merely lengthens it.
Ischemia
• Transmural ischemia
– is said to exist when ischemia extends subepicardially. This process has a more visible effect on recovery of subepicardial cells compared with subendocardial cells. Recovery is more delayed in the subepicardial layers, and the subendocardial muscle fibers seem to recover first.
Ischemia
• Hyperacute T-Waves– Results from subendocardial ischemia– Symmetrical & tall– Wide with blunt peak (unlike Hyperkalemia)– Present for about first 30 min. of AMI
• Inverted T-waves– Results from transmural ischemia
Ischemia
Asymmetrical
Symmetrical
Ischemia
Ischemia-Mimic
Peaked T-Waves
Inverted T-Waves
Hyperkalemia STE-Mimic
Injury
• Injury to the myocardial cells results when the ischemic process is more severe.
• In patients with coronary artery disease, ischemia, injury and myocardial infarction of different areas frequently coexist, producing mixed and complex ECG patterns.
Injury
• ST-Depression– Subendocardial
• ST-Elevation – Subepicardial– Transmural.
Injury
Injury
ST-Depression
ST-Elevation
Injury-Mimic
ST-Elevation
Hyperkalemia STE-Mimic
Infarct
• The term infarction describes necrosis or death of myocardial cells.
• Atherosclerotic heart disease is the most common underlying cause of myocardial infarction.
• The left ventricle is the predominant site for infarction; however, right ventricular infarction occasionally coexists with infarction of the inferior wall of the left ventricle.
Infarct
• During acute myocardial infarction, the central area of necrosis is generally surrounded by an area of injury, which in turn is surrounded by an area of ischemia.
• Various stages of myocardial damage can coexist.
• The distinction between ischemia and necrosis is whether the phenomenon is reversible.
Infarct
• Pathological Q-waves– Wider than 0.04sec / 40ms (1 small box)– Deeper than 25% the height of R-Wave
Reciprocal Changes
• ST-Depression found in leads opposite of those with ST-Elevation is considered to be a reciprocal change. – This is caused by a view from the opposite
direction.
Site Facing Reciprocal
Septal V1, V2 V7, V8, V9
Anterior V3, V4 None
Lateral I, aVL, V5, V6 II, III, aVF
Inferior II, III, aVF I, aVL
Posterior V7, V8, V9 V1, V2
Reciprocal Changes
QuickTime™ and a decompressor
are needed to see this picture.
Inferior Injury
Reciprocal ST-Depression
Location of MI
Inferior Wall
Anterior Wall
Lateral Wall
Septal
Location of MI
Left Ventricle
Right Ventricle
Antero-Septal Wall
• Leads V1 & V2 view the septal wallLeads V1 & V2 view the septal wall
• Leads V3 & V4 view the anterior wallLeads V3 & V4 view the anterior wall
LV
RV
V1 V2 V3V4
V5
V6
Septal Wall
Anterior Wall
• Leads V3 & V4 view the Anterior Wall
LV
RV
V1 V2 V3V4
V5
V6
Anterior Wall
Lateral Wall
• Leads I, aVL, V5 & V6 view the lateral wall
LV
RV
V1 V2 V3V4
V5
V6
Lateral Wall
Inferior Wall
Inferior Wall
Inferior Wall
Inferior Wall
Right Ventricular Wall
• With a proximal occlusion of the RCA, a right ventricular infarct is possible.– Hypotension is most common finding.– Right-sided placement of V3 & V4 can be used to
view the right ventricle for ST-Elevation.• V4R is most sensitive lead for right-sided changes. • QRS complexes and ST-Elevation may be of much
lesser amplitude in right-sided leads.
Right Ventricular Wall
• Hypotension is most common assessment finding with RV-Infarction.– NTG should be used very conservatively– Fluids should be administered if unstable
• ST-Elevation in lead III > than STE in lead II is very specific for RV-Infarction
Right Ventricular Wall
V4V3
Move V3 & V4 to mirrored position on right side of chest to obtain V3R & V4R.
The same can be done for V5 & V6.
Right Ventricular Wall
Always make sure to denote the leads you change.
I aVR V1 V4R
II aVL V2 V7
III aVF V3R V6
Posterior Wall
• Dominant RCA– When the RCA supplies the posterior descending
coronary artery– 85% of people have dominant RCA
• Dominant Circumflex– When LCx supplies the posterior descending
coronary artery– 15% of people have dominant circumflex
Posterior Wall
• The reciprocal leads are V1 & V2• ST-depression in V1 & V2 may actually be
representing ST-elevation of the posterior wall
• Tall R-waves in V1 & V2 may actually be representing pathological Q-waves of the posterior wall
Posterior Wall
V1/V2
To identify a posterior wall MI, a technique commonly taught is to pretend you are looking at the complex upside-down through a mirror
Posterior Wall
Move V4 to V7 - posterior axillary line Move V5 to V8 - midscapularMove V6 to V9 paraspinal
I aVR V1 V7
II aVL V2 V8
III aVF V3 V9
V7, V8, V9
LBBB With MI
Modified Sgarbossa’s criteria• Any concordant ST-Elevation!• ST-Elevation > 25% of depth of preceding S-
Wave = MI– This is an advanced skill, and is completely reliant
on the T-wave discordance found with a LBBB
• This same criteria may be used with paced rhythms
Sgarbossa’s Criteria
Sgarbossa’s Criteria
Other MI Findings
• If ECG print out does not read ***Acute MI***, it is highly unlikely that the capture meets STEMI criteria.– It is possible that the 12-lead is not a true STEMI even with
the “Acute AMI” reading.
• Wellen’s phenomenon - Biphasic or inverted T-waves (Most commonly in V2 & V3), precursor to AMI from LAD stenosis.
Practice
RBBB With MI
Practice
Antero-septal MI
Antero-septal MI
A
B
Practice
Anterior MI
Practice
A
B
Inferior MI
Practice
Inferior MI
Practice
Antero-septal MI
Practice
RBBB, Inferior MI
Practice
Practice
RBBB
No ST-Elevation!
Practice
29 y/o Male
WPW
29 y/o Male
Practice
B
A
Practice
Practice
A
B
R
R
Practice
A
B
R
R
Inferior-Posterior MI
A
B
R
R
Practice
Antero-septal MI
A
B
Practice
Bigeminy Anterior MI
Practice
Antero-septal-lateral MI
Practice Scenarios
“Always consider the company it keeps”
- Dr. Thomas Garcia
Practice Scenario 1
• You respond to an 87 year-old female who states that she awoke with “a fast heart rate”.
• She states that she has had this condition for over 50 years, and denies any pain or dyspnea.
• She has had heart surgery in the past.
Practice Scenario 1
• No abnormal physical exam findings• BP: 156/74 • HR: 124 irregularly irregular• O2 Sat:96% on room air
Practice Scenario 1
Practice Scenario 2
• You respond to a 51 year-old female who reportedly became unconscious and slumped over in a chair.
• Family states that she has been unconscious for 5 minutes.
• She has a history of hypertension and takes Xanax and hydrochlorothiazide.
Practice Scenario 2
• She is flushed and diaphoretic • She is awake but disoriented
• BP: 180/120• HR: 110 Regular • Respirations: 16 • O2 Sat: 95%
Practice Scenario 2
Practice Scenario 3
• You respond to a 94 year-old female in a nursing home.
• She had a syncopal episode per the LPN, and is currently complaining of unlocalized pain.
Practice Scenario 3
• She is pale but dry• BP: 142/57 • HR: 88 • Respirations: 24 • O2 Sat: 88% on High-flow O2
Practice Scenario 3
Practice Scenario 3
Practice
Trigeminal PVCs
Possible Antero-septal Infarct
Trigeminal PVCs
Trigeminal PVCs
Lesson 5
• This concludes lesson 5
• Please review the course materials