W10 D2 - 12 Lead ECG

Question 1

How many leads are in frontal and horizontal leads?

Answer 1

6 frontal plane leads
* front and back half
* 3 bipolar: lead I-III Einthoven’s triangle
* 3 unipolar: lead aVR, VL, VF

6 horizontal plane leads
* top and bottom half
* 6 unipolar: V1-V6

Question 2

What is Einthoven’s triangle?

Answer 2

Frontal plane leads I-III form a triangle from right to left arm to left foot

Question 3

Which portion of the heart is lead I, II, II looking at?

frontal planes

Answer 3

Lead I - lateral portions
Lead II - right inferior ?
Lead III - left inferior ?

Question 4

What portion of the heart are V1-6 looking at?

horizontal plane

Answer 4

V1- anterior septum (middle)
V2 - anterior septum
V3 - anterior LV
V4 - anterior LV
V5 - lateral, 30 degrees
V6 - lateral, 0 degrees direct side view

V1-4: anterior views
V5-6: lateral (left) side

Question 5

What leads are looking at the lateral portions of the heart?

Answer 5

AVL
Lead I
V5
V6

Question 6

What leads are looking at the inferior portion of the heart?

Answer 6

Lead II
Lead III
AVF

Question 7

What leads are looking at the anterior portion of the heart?

Answer 7

V1-V4

Question 9

What is a vector?

Answer 9

An arrow which provides size/magnitude and direction of the electrical activity in the heart

Question 10

Which coronary artery perfuses the lateral side of the heart?

What leads does this include?

Answer 10

Circumflex
via V5, V6, Lead I, aVL

Question 11

Which coronary artery perfuses the inferior portion of the heart?

What leads does this inlcude?

Answer 11

RCA
via leads II, III, AVF

Question 12

Which coronary artery supplies the anterior portion of the heart?

What leads does this include?

Answer 12

LAD
via V1 & V2 (septum)
V3 & V4 (LV)

Question 13

Summarize the coronary artery supplies and their associated lead changes

Answer 13

LAD - anterior/septum
* V1-2 septum
* V3-4 ventricle

Circumflex - lateral (some posterior)
* V5-6
* Lead I
* aVL

RCA - inferior, posterior, RV
* inferior: lead II, III, aVF
* posterior: tall R waves & ST depression in V1 & V2
* RV: ST elevation in V4 (for STEMI only)

Question 14

What is a pathological Q wave?

Answer 14

A Q wave that is more than 1/4 the size of the R wave
* indicates necrotic tissue

Question 15

What does an ST elevation indicate?

Answer 15

STEMI - complete block of vessel
* requires immediate attention
* localized to anatomical groups on ECG
* full thickness damage to myocardium

Question 16

What is R wave progression? Where is the largest?

Answer 16

The R wave becomes taller and the S wave becomes smaller through V1-V6 as the views wrap around the heart
* the largest should be at the apex V4/V5
* if its not, the electrical activity is early or late (thicker muscle or poor lead placement)

Question 17

What is ventricular axis & what does it tell us?

Answer 17

The average direction of ventricles should be towards the + pole of lead II
* indicates heart disease if there are deviations from the normal direction
* extreme right or left deviation = no mans land in the RUQ of heart

Question 18

How do you determine axis deviation?

Question 19

What happens during a RBBB?
What does it look like on ECG?

Answer 19

Septum depol. left to right; Left ventricle depolarizes first, right follows slowly
* best seen in V1
* therefore QRS willl be wide
* rSR pattern, bunny ears
* ST/T waves will be abnormal, NOT MI

Question 20

What happens during a LBBB?
What does it look like on ECG?

Answer 20

Septum depol. right to left; Right ventricle depolarizes first, left follows slowly
* best seen in V6
* therefore QRS willl be wide
* R wave is wide, sometimes bump
* ST/T waves will be abnormal, NOT MI

Question 21

What does a down sloping ST depression indicate?

Answer 21

NSTEMI - partial block of vessel
* can also be horizontal ST depression
* only partial thickness damage to subendocardium
* widespread changes; does not localize on ECG

Question 22

As MI evolves, what will you see in ECG? Why?

early, middle, late, or old detection

Answer 22

Hyperacute T waves
* early sign of oxygen deprivation

ST elevation
* within hours
* may be w/ tall or inverted T waves
* cell injury/damage is aparent but reversible

STEMI w/ pathological Q waves
* Q waves are more than 1/4 R wave
* 1-12 hours
* some cells dying

Old infarct
* takes up to 2 weeks
* ST segment returns to normal
* pathological Q wave remains as there is none reversible cell death

Question 23

Which are the reciprocal leads? (mirror image)

Answer 23

Reciprocal lead is a different view of the heart which reverses the ECG info

PAILS
ST elevation in ____ will show as depression in ____
* Posterior … anterior
* Anterior … inferior
* Inferior … lateral
* Lateral … septal or inferior

Question 24

What is the treatment for RV infarction? Why?

Answer 24

Increase preload via bolus +++ before inotrope/pressors
* need to stretch ventricle out as much as possible

Question 25

How do you identify a posterior MI on ECG?

Answer 25

Use a 15 lead ECG; place leads 7,8,9 on the left back, 5th intercoastal space
* posterior MI = ST elevation in these leads
* if unable to do 15 lead, use reciprocal: ST depression in V1,2,3 and tall R waves

Question 26

Why is AVR different?

Answer 26

Normal ECG - negative deflections only

Question 27

What MI would include aVR ECG changes?

Answer 27

Left main or proximal left main artery occlusion
* wide spread ST depression with ST elevation in aVR greater than V1

Question 28

How do you assess 12 lead ECG?

Answer 28

1. Identify rate and rhythm
2. Find Axis
3. Is the QRS wide or not?
4. If yes check for BBB
   * RBBB = V1 - rSR pattern
   * LBBB = V6 - wide or notched

~5.If no, check for ischemia / MIs
* NSTEMI - ST depression / inverted T waves
* STEMI - ST elevation in at least two leads from same group and pathological Q waves