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12-Lead 12-Lead ElectrocardiographyElectrocardiography
a comprehensive course
Adam Thompson, EMT-P, A.S.Adam Thompson, EMT-P, A.S.
Ischemia,
Injury, &
Infarct
(Part 3)
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
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 V5
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
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.
Part 3
• Next we will look at some examples…
