ECG Interpretation

Question 1

What does one small square on an ECG represent?

Answer 1

1mm (0.04 seconds)

Question 2

What does one large square on an ECG represent?

Answer 2

5mm (0.2 seconds)

Question 3

How do you calculate a heart rate from an ECG?

Answer 3

If regular - count number of large squares between R-R interval and divide 300 by this number

If irregular - count number of QRS complexes on one strip and times by 6

Question 4

How do you determine normal cardiac axis from an ECG?

Answer 4

Lead I, II and III are all positive
Lead II is the most positive
Lead avR is the most negative

Question 5

How do you determine right axis deviation from an ECG?

Answer 5

Lead I is negative
Lead II and III are positive
Most positive is lead III

Question 6

What is the most common cause of right axis deviation?

Answer 6

Lead I is positive
Lead II and III are negative
Lead I is most positive

Usually due to conduction abnormalities

Question 7

What most commonly causes an absent P wave?

Answer 7

Atrial fibrillation

Question 8

How long should a PR interval be?

Answer 8

3-5 small squares

Should be no more than one large square (0.2s)

Question 9

What does a prolonged PR interval suggest?

Answer 9

Heart block

Question 10

What is first degree heart block? How is it managed?

Answer 10

Prolonged PR interval

No management needed

Question 11

What is second degree heart block type 1?

How is it managed?

Answer 11

Progressive prolongation of the PR interval until a dropped QRS

No management needed

Question 12

What is second degree heart block Mobitz type 2? How is it managed?

Answer 12

Constant prolongation of PR interval with intermittently dropped QRS

Management = Permanent pacemaker

Question 13

What is third degree heart block?

Answer 13

No association between PR interval and QRS complex

QRS complex= usually regular

Management= permanent pacemaker

Question 14

What is a significant ST elevation?

Answer 14

> 1mm in 2 or more limb leads

>2mm In 2 or more chest leads

Question 15

What does ST elevation in leads V1-V4 signify?

Answer 15

Anteroseptal MI

LAD

Question 16

What does ST elevation in I, avL, V5 and V6 signify?

Answer 16

Lateral MI

Left circumflex artery

Question 17

What does ST elevation in leads II, III, aVF indicate?

Answer 17

Inferior MI

Right coronary artery

Question 18

X

Answer 18

X

Question 19

Which electrolyte disturbances can cause long QT syndrome ?

Answer 19

Hypocalcaemia
Hypokalaemia 
Hypomagmasaemia
Hypothermia
Hypothyroidism

Question 20

Which drugs can cause long QT syndrome ?

Answer 20

METHCATS
Methadone/Methotrexate
Erythromycin
Terfenadine
Haloperidol
Citalopram
Amiodarone
Tricyclics
Sotalol

Question 21

How do you determine left axis deviation from an ECG?

Answer 21

Lead I is positive
Lead II and III are negative
Lead I is most positive

Usually due to conduction abnormalities

Question 22

Which electrolyte abnormality is associated with tall T waves?

Answer 22

Hyperkalaemia

Question 23

What ECG changes are seen in hyperkalaemia?

Answer 23

Tall tented T waves
Widened flattened P wave
Prolonged PR interval
Broad QRS

Severe:
Sinusoidal wave pattern
V fib

Question 24

What is seen on ECG in left bundle branch block?

Answer 24

Wide QRS complex
WiLLiaM
V1 = W = rS
V6 = M

Question 25

What is seen on ECG in right bundle branch block?

Answer 25

Wide QRS complex V1 = M = RSR V6 = W = rS MaRRoW

Question 26

Which leads is it normal for the T wave to be inverted?

Answer 26

Lead V1 and avR Can also be normal in lead I, avL and V6 Can also be normal in lead III

Question 27

What are the two types of tachycardia?

Answer 27

Narrow complex and broad complex

Question 28

What are the two types of ventricular tachycardia?

Answer 28

Monomorphic and polymorphic

Question 29

What is the main cause of monomorphic ventricular tachycardia?

Answer 29

Myocardial infarction

Question 30

What is an example of polymorphic ventricular tachycardia?

Answer 30

Torsades de pointes (caused by long QT)

Question 31

How does atrial fibrillation present on an ECG?

Answer 31

Irregularly irregular rhythm Absence of P wave Narrow complex

Question 32

How does hypokalaemia present on an ECG?

Answer 32

U waves Small/absent T waves Prolonged PR interval (same as hyperkalaemia)

Question 33

How is Wolff-Parkinson White Syndrome seen on an ECG?

Answer 33

Short PR interval Broad QRS Delta wave Left or right axis deviation Pseudo-Q waves

Question 34

How can Digoxin use affect an ECG?

Answer 34

U waves Short QT interval Downward sloping ST depression T wave flattening Arrhythmias - AV block

Question 35

What are causes of RBBB?

Answer 35

Right ventricular hypertrophy PE MI

Question 36

How does hypothermia present on an ECG?

Answer 36

Jesus Quist It's Bloody Freezing J waves QT prolongation irregular Bradycardia First degree block Also: Torsades de pointes

Question 37

How can Wolff-Parkinson White be treated?

Answer 37

Radiofrequency ablation of the accessory pathway

Question 38

What is a ventricular ectopic?

Answer 38

A premature ventricular beat causes by random electrical discharges Seen on ECG as an individual random broad QRS complex

Question 39

What ECG change is seen in cardiac tamponade?

Answer 39

Electrical alternans (alternating QRS amplitude)

Question 40

How is torsades de pointes treated?

Answer 40

IV Magnesium sulfate, Cardioversion

Question 41

How can raised ICP show on an ECG?

Answer 41

Long QT

Question 42

What ECG change can be seen in rheumatic fever?

Answer 42

P mitrale due to mitral stenosis Prolonged PR

Question 43

What are indications for cardiac re-synchronisation therapy in heart failure?

Answer 43

Widened QRS complex on ECG Usually last resort

Question 44

What is normal QT length?

Answer 44

No more than 11 small squares

Question 45

What is normal QRS length?

Answer 45

No more than 0.12s (3 small squares) Normal = around 2 small squares

Question 46

What is a bi-fascicular block?

Answer 46

RBBB + Left axis deviation

Question 47

What is a tri-fascicular block?

Answer 47

RBBB + Left axis deviation + 1st degree heart block

Question 48

What is the difference between 2:1 and 3:1 atrial flutter?

Answer 48

2: 1 = 2 flutters to each QRS 3: 1 = 3 flutters to each QRS

Question 49

What precipitates Torsades des Pointes?

Answer 49

Long QT

Question 50

How is a posterior MI seen on ECG?

Answer 50

``` Reciprocal changes in V1-V3 : ST depression Tall broad R waves Upright T waves Dominant R wave in V2 ```

Question 51

In which leads do you get reciprocal changes (ST depression) for each type of STEMI?

Answer 51

PAILI (Posterior, anterior, inferior, lateral, inferior) You get reciprocal changes in area after E.g. Anterior MI you get inferior reciprocal changes

Question 52

Which ECG leads are the limb leads?

Answer 52

I, II, III | avR, avL, avF

Question 53

What can be the first sign of a STEMI on ECG?

Answer 53

Hyperacute T waves