Heart block

Question 1

What are the 2 types of 2nd degree AV block?

Answer 1

Mobitz type I- Progressive prolongation of AV node conduction resulting in one atrial impulse failing to be conducted through AV node

Mobitz type II- Intermittent or regular failure of conduction through the AV node

Question 1

What is 1st degree AV block?

Answer 1

Prolonged conduction through the AV node

Question 2

What is 3rd degree (complete) AV block?

Answer 2

No relationship between atrial and ventricular contraction

Question 3

What are causes of heart block? (3)

Answer 3

• Drugs e.g. digoxin
• Metabolic e.g. Hyperkalaemia
  MI- Right coronary artery occlusion which supplies AV node

Question 4

Which types of heart block are usually asymptomatic? (2)

Answer 4

• 1st degree
• 2nd degree

Question 5

Which types of heart block can cause Stokes-Adams attacks? (2)

Answer 5

• Mobitz type II
• 3rd degree heart block

Question 6

What is stokes-adams? and cf?

Answer 6

temporary lack of blood flow to the brain
- Syncope
- Dizziness
- Palpitations
- Chest pain

Bizarre, wide, inverted T waves

Question 7

What can Mobitz type II and 3rd degree heart block show signs of?

Answer 7

Signs of reduced cardiac output, hypotension

Question 8

List clinical features of complete heart block (3)

Answer 8

• JVP may show cannon A waves
• Syncope
• Regular bradycardia → 30-50 bpm

Question 9

What does ECG show in 1st degree heart block?

Answer 9

Fixed prolonged PR interval (more than 3-5 small squares)(0.04s/40ms = 1 small square)

Question 10

What is a prolonged PR interval and prominent U waves a sign of?

Answer 10

Hypokalaemia

Question 11

What other signs of hypokalaemia are there? (2)

Answer 11

. prolonged PR interval and prominent U waves
- Flattened T waves
- ST segment depression

Question 12

Name a cause of hypokalaemia

Answer 12

Diuretic use e.g. Thiazide diuretic like Bendroflumethiazide

Question 13

What does ECG show in Mobitz type I?

Answer 13

Progressively prolonged PR interval, then eventually dropped beat

Question 14

What does ECG show in Mobitz type II?

Answer 14

PR interval is constant but intermittently a P wave is not followed by a QRS

Question 15

What does ECG show in complete heart block?

Answer 15

No relationship between p waves and QRS complexes - complete AV dissociation

Question 16

What is the definitive management for chronic block?

Answer 16

• Permanent pacemaker
• Mobitz II is an indication for a pacemaker
• Pacemaker ECG

Question 17

What is the acute management for acute block?

Answer 17

IV atropine 500mg

• Used for bradycardias to speed up the heart
• Would be used in the acute setting of symptomatic bradycardias or in those with low blood pressure

max dose you can give is 3mg

Question 18

if iv atropine isn’t working, what can you give?

Answer 18

• Transcutaneous pacing
• isoprenaline
• adrenaline
• aminophylline
• glucagon (if beta blocker of calcium channel blocker overdose)

Transvenous pacing

Question 19

What are the risk factors for asystole in bradycardia? (4)

Answer 19

• Mobitz 2
• complete heart block patients w/ broad QRS
• Recent asystole
• Ventricular pause >3 seconds

Managed by Transvenous pacing