ECGs 2

Question 1

Which ECG leads look at the inferior side of the heart?

Answer 1

Lead II
Lead III
aVF

Question 2

Which ECG leads look at the lateral side of the heart?

Answer 2

Lead I
aVL
V5
V6

Question 3

Which ECG leads look at the anterior side of the heart?

Answer 3

V1-V4

Question 4

Which ECG leads look at the right side of the heart?

Answer 4

V1
V2 (partly)

Question 5

What is the first rule of ECGs?

Answer 5

The PR interval is between 0.12 & 0.2 sec (3 -5 small squares)

Question 6

How long should the PR interval be?

Answer 6

Between 0.12 & 0.2 sec (3 -5 small squares)

-Rule 1

Question 7

What is a long PR interval suggestive of?

Answer 7

First degree heart block

Question 8

What is a short PR interval a sign of?

Answer 8

Pre-excitation (Accessory pathway)
OR
AV nodal (Junctional) rythm

Question 9

What is the second rule of ECGs?

Answer 9

The QRS duration is <0.12 sec (<3 small squares)

Question 10

How wide should the QRS complex be?

Answer 10

<0.12 sec (<3 small squares)

-Rule 2

Question 11

What can cause a wide QRS?

Answer 11

Broad complexes may be ventricular in origin or due to aberrant conduction secondary to:

Bundle branch block (RBBB or LBBB)
Hyperkalaemia
Poisoning with sodium-channel blocking agents (e.g. tricyclic antidepressants)
Pre-excitation (i.e. Wolff-Parkinson-White syndrome)
Ventricular pacing
Hypothermia
Intermittent aberrancy (e.g. rate-related aberrancy)

Question 12

What are the complex morphologies of LBBB shown in V1 and V6?

Answer 12

V1can be:
-‘W’ shaped
-Small r wave with deep S
-Absent R wave and deep Q wave

V6 can be:
-‘M’ shaped
-Notched
-Broad and monophasic
-RS pattern

Question 13

What axis deviation is seen with LBBB?

Answer 13

Left

Question 14

What causes narrow QRS complexes?

Answer 14

Narrow (supraventricular) complexes arise from three main places:

-Sino-atrial node (= normal P wave)

-Atria (= abnormal P wave / flutter wave / fibrillatory wave)

-AV node / junction (= either no P wave or an abnormal P wave with a PR interval < 120 ms)

Question 15

If a narrow complex rythm is present with a normal P wave where is it most likely to originate from?

Answer 15

The SA node

Question 16

If a narrow complex rythm is present with abnormal P waves where is it most likely to originate from?

Answer 16

Abnormal OR fluttering OR fibrillating P wave:
Atria

Abnormal P wave with a short PR (<120ms):
AV node / junction

Question 17

If a narrow complex rythm is present with absent P waves where is it most likely to originate from?

Answer 17

AV node/junction

Question 18

What is the third rule of ECGs?

Answer 18

The QRS complex should be predominantly upright in leads I & II

Question 19

In which leads should the QRS complex be predominantly upright?

Answer 19

Leads I & II

-Rule 3

Question 20

When are Q waves considered pathological?

Answer 20

If they are:

> 40 ms (1 mm) wide
2 mm deep
25% of depth of QRS complex
Seen in leads V1-3

Question 21

What are pathological P waves usually a sign of?

Answer 21

Pathological Q waves usually indicate current or prior myocardial infarction, especially when present with ST elevation and/or T wave inversion.

Differential diagnoses include:
- Myocardial infarction
-Cardiomyopathies (Hypertrophic (HCM), infiltrative myocardial disease)
-Rotation of the heart (Extreme clockwise or counter-clockwise rotation)

Question 22

In which leads can Q waves be normal?

Answer 22

Small Q waves are normal in most leads

Deeper Q waves (>2 mm) may be seen in leads III and aVR as a normal variant

Question 23

Where are Q waves not normally present (in the absence of pathologies)?

Answer 23

V1-V3

Question 24

What can predominantly negative QRS complexes in some chest leads be caused by?

Answer 24

Axis deviation - caused by a number of pathologies, can be normal variants.

Question 25

What is the fourth rule of ECGs?

Answer 25

QRS & T waves tend to have the same general direction in the limb leads

Question 26

In which leads should the QRS and T waves have the same general direction?

Answer 26

The limb leads -Rule 4

Question 27

What are the characteristics of normal T waves?

Answer 27

Upright in all leads except aVR and V1 Amplitude < 5mm in limb leads, < 10mm in precordial leads (10mm males, 8mm females) Duration relates to QT interval

Question 28

What amplitude is considered abnormal for T waves?

Answer 28

More than 10mm in males and 8mm in females

Question 29

What is the fifth rule of ECGs?

Answer 29

Confirm that aVR is negative (if not check limb lead placement)

Question 30

What is the sixth rule of ECGs?

Answer 30

The R wave in the precordial leads must grow from V1 to at least V4

Question 31

How is R wave progression assessed on ECGs?

Answer 31

The R wave should grow from V1 to at least V4 -Rule 6

Question 32

What can cause poor R wave progression?

Answer 32

Prior anteroseptal MI Left Ventricular Hypertrophy (LVH) Right Ventricular Hypertrophy (RVH) Dilated cardiomyopathy May be a normal variant "Crap R, crap heart"

Question 33

What is the seventh rule of ECGs?

Answer 33

The ST segment should start isoelectric except in V1 & V2 where it may be slightly elevated

Question 34

In which leads may there be some **slight** normal ST elevation?

Answer 34

V1 & V2 -Rule 7

Question 35

What is the ST elevation criterea for MIs?

Answer 35

New ST segment elevation at the J point in at least two contiguous leads of ≥ 2 mm in men or ≥1.5 mm in women in leads V2-V3 and/or of ≥ 1 mm in other contiguous chest leads or the limb leads.

Question 36

How much ST elevation are you looking for in leads V2-V3?

Answer 36

≥ 2 mm in men or ≥1.5 mm

Question 37

How much ST elevation are you looking for in contiguous chest leads **other than V2-V3** or the limb leads?

Answer 37

≥ 1 mm in men and women

Question 38

What reciprical changes might you expect to have in an anterior STEMI?

Answer 38

ST depression in inferior leads (mainly III and aVF)

Question 39

In which MIs might you **not** see reciprical changes?

Answer 39

Anterior STEMIs that do not involve high lateral leads.

Question 40

What is the eighth rule of ECGs?

Answer 40

The P waves should be upright in I, II & V2 to V6

Question 41

In which leads are atrial abnormalities most easily seen, why?

Answer 41

Atrial abnormalities are most easily seen in the inferior leads (II, III and aVF) and lead V1, as the P waves are most prominent in these leads.