Heart Block

Question 1

What are the types of atrio-ventricular block?

Answer 1

• 1st degree
• 2nd degree
• complete heart block

Question 2

What are the types of bundle branch block?

Answer 2

• Left bundle branch block

* Right bundle branch block

Question 3

What does first degree heart block mean?
What does it show on an ECG?
Where does the block occur?

Answer 3

• Every atrial depolarisation followed by conduction to the ventricles but with delay
• PR interval >120ms (delayed)
• The block is occurring between the SA node and the AV node (i.e. within the atrium)

Question 4

What does Mobitz 1 2nd degree heart block mean?
What does it show on an ECG?
Where does the block occur?

Answer 4

• When some of the P waves conducts and others do not
• ECG: PR interval slowly increase the there is a dropped QRS complex
• Block occurs within the AV node

Question 5

What does Mobitz 2 2nd degree heart block mean?
What does it show on the ECG?
Where does the block occur?

Answer 5

• When some of the P waves conducts and others do not
• ECG: PR interval prolonged but fixed with dropped beats
• Block occurs after the AV node in the bundle of His or Purkinje fibres

Question 6

What does complete heart block mean?
What does it show on the ECG?
Where does the block occur?

Answer 6

• Complete absence of AV function
• P wave and QRS are completely unrelates
• Occurs anywhere from the AV node down causing complete blockage of conduction

Question 7

What is left bundle branch block?

Answer 7

Activation of the left ventricle is delayed, causing the left ventricle to contract after the right

Question 8

What is right bundle branch block?

Answer 8

Activation of the right ventricle is delayed, causing the right ventricle to contract after the left

Question 9

What ECG leads do you look at when trying to assess for bundle branch block?

Answer 9

V1 and V6

Question 10

What findings are seen on an ECG in left bundle branch block?

Answer 10

WiLLiam

• V1 shows a W in the QRS
• V6 shows a M in the QRS complex
• Broad QRS complex >120ms
• Absence of Q wave in lateral leads

Question 11

What findings are seen on an ECG in right bundle branch block?

Answer 11

MaRRoW

• V1 shows a M in QRS
• V6 show a W in QRS
• Broach QRS complex >120ms

Question 12

What are the causes of complete heart block?

Answer 12

• Congenital: structural heart defect
• Idiopathic fibrosis
• Ischaemic heart disease
• Cardiac surgery
• Infections: endocarditis, Chagas disease, SLE
• Drug induced: Digoxin, beta blockers, amiodarone, Ca2+ channel blockers non dihydropyridine

Question 13

Presentation of complete heart block?

Answer 13

• Fainting/collapse
• Dysponea
• Fatigue
• Confusions
• Chest pain
• Palpitations
• Bradycardia

Question 14

What investigations should you do for complete heart block?

Answer 14

• ECG

* Echo

Question 15

What are the management steps of complete heart block?

Answer 15

• AV block due to transient cause may respond to IV atropine
• Trancutaneous pacing (Defibrillate)
• Pacemaker fitted for chronic cases

Question 16

Acute adult bradycardia management steps:

Consider worst case scenario

Answer 16

1. A-E assessment
2. Adverse features? shock, syncope, MI, Heart failure

YES:
>Atropine 500mcg IV
>Response? 
>No
>Further Atropine 500mcg until 3mg 
>Trancutaneous pacing 
>Adrenaline or isoprenaline 

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