ECG

Question 1

How long/wide is a normal PR interval?

Answer 1

3-5 small squares (0.12-0.20 sec)

Question 2

How deep/wide is a normal Q wave? What leads is a Q wave normally seen in?

Answer 2

• <0.03 sec
• <1/3 the height of the following R wave
• Normally seen in I, aVL (sometimes V1-2)

Question 3

How long is the normal QT interval? What is the formula for the rate-corrected variant (QTc)

Answer 3

• 0.410 sec (<1/2 R-R)
• QTc = QT + 1.75(ventricular rate - 60)

Question 4

How wide is a normal QRS complex? How tall in the limb leads?

Answer 4

• 0.06 - 0.11 sec (1.5 - 3 small squares)
• > 5 mm tall in the limb leads

Question 5

What direction isthe RA depolarisation vector?

Answer 5

Right, down, posterior

Question 6

What direction is the LA depolarisation vector?

Answer 6

Left, down , back

Question 7

What direction is the septal depolarisation vector?

Answer 7

Right to left

Question 8

What direction is the main ventricular depolarisation vector?

Answer 8

Inferior, posterior, left

Question 9

What direction is the late ventricular depolarisation vector?

Answer 9

Up, right and posterior

Question 10

What are the ECG characteristics of a wandering atrial pacemaker? How is it distinguished from a multifocal atrial tachycardia?

Answer 10

• < 100 bpm with at least 3 different P wave morphologies
• MAT - > 100 bpm

Question 11

What are the ECG characteristics of atrial flutter?

Answer 11

Regular saw-toothed flutter waves with regular ventricular response

Question 12

What are the ECG characteristics of atrial fibrillation?

Answer 12

• No discernable P waves, random QRS

Question 13

How fast is a junctionally-paced rhythm on an ECG? A ventricular paced rhythm?

Answer 13

• 40-60 bpm
• 20-40 bpm

Question 14

What is 1st degree heart block?

Answer 14

• Prolonged PR interval (> 0.20 or 5 small squares)

Question 15

What is Mobitz I second-degree heart block?

Answer 15

• Lengthening PR until a beat is dropped after a P wave

Question 16

What is Mobitz II second-degree heart block?

Answer 16

• Fixed PR interval and P:QRS ratio, but a QRS is dropped in a regular pattern after a P wave

Question 17

What is third-degree heart block? How is it different to AV dissociation?

Answer 17

• Different P and QRS rates
• AV dissociation if rate is the same

Question 18

What might cause an ST segment to be concave-up shaped?

Answer 18

• Pericarditis
• Early repolarisation
• Strain

Question 19

What might cause an ST segment to be concave-down shaped?

Answer 19

Strain

Question 20

What might cause an ST segment to be flat and depressed?

Answer 20

Subendocardial ischaemia

Question 21

What might cause an ST segment to be flat and elevated?

Answer 21

Myocardial injury

Question 22

What might cause an ST segment to tombstone?

Answer 22

• Infarction
• Aneurysm

Question 23

What is the normal shape and height of T waves on an ECG?

Answer 23

• Asymmetrical
• < 6 mm in limb leads
• < 12 mm in precordial leads

Question 24

What might be the cause of tall, peaked, narrow T waves on an ECG?

Answer 24

Hyperkalaemia

Question 25

What can tall, symmetrical T waves signify on an ECG?

Answer 25

Injury

Question 26

What are the ECG characteristics of pericarditis?

Answer 26

* Global ST elevation * Concave-up ST segments * PR depression * Tachycardia

Question 27

What are the ECG characteristics of a right-bundle-branch block?

Answer 27

* QRS \>= 0.12 sec * Slurred S in I, V6 * Positive complexes in V1 and RSR' morphology

Question 28

What are the ECG characteristics of a left-bundle-branch block?

Answer 28

* My, what an ugly 'gram * QRS \>= 0.12 sec * Broad R in V1, V6 * Broad S complex in V1

Question 29

What are the ECG characteristics of a left anterior hemiblock?

Answer 29

* LAD -30 to -90 * qR or R complex in I * rS in III

Question 30

What are the ECG characteristics of a left posterior hemiblock?

Answer 30

* Axis 90-180 * S complex in I * q complex in III * **No RAE or RVH present**

Question 31

What are the ECG characteristics of a left atrial enlargement?

Answer 31

* P wave \> 0.12 sec and notched greater than 0.04 in limb leads

Question 32

What are the ECG characteristics of a right atrial enlargement?

Answer 32

* Peaked P wave (\> 2.5 mm) in limb leads

Question 33

What are the ECG characteristics of LV hypertrophy?

Answer 33

* (S wave in V1 or V2) + (R wave in V5 or V6) \> 35 mm * AND/OR * any precordial \> 45 mm * R wave in aVL \>= 11mm * R wave in I \>= 12 mm * R wave in aVF \>= 20 mm

Question 34

What are the ECG characteristics of a RV hypertrophy?

Answer 34

* R:S \>=1 in V1 and/or V2