Heart block

Question 1

What is the classification of heart block

Answer 1

First degree
Second degree type I (Wenckebach or Mobitz I)
Second degree type II (Mobitz II)
Third degree (complete), no impulses passed from atria to ventricles

Question 2

Define Heart block

Answer 2

Impaired (delayed or absent) conduction of electrical impulses from atria to ventricles

Question 3

Aetiology of heart block

Answer 3

First/second degree: AV node block, usually due to high vagal tone
- tonic elevation (young, athletic)
- transient: valsalva, ischaemia (inferior), endotracheal suctioning
- Drugs: beta-blockers, CCBs, adenosine, digoxin

Second/third: His-Purkinje system block
- IHD (inferior)
- Fibrosis or calcification of conduction system
- Valve calcification
- Infiltration (abscesses, granulomas, tumours, parasites)
- Cardiac surgery/trauma
- digoxin toxicity

Question 4

Symptoms of heart block

Answer 4

Syncope/Pre-syncope
Fatigue
Chest pain
Palpitations
Nausea or vomiting

Question 5

Signs of heart block of examination

Answer 5

Bradycardia <40bpm
High blood pressure, wide pulse pressure
Cannon A wave in the JVP (complete)
Hypoxaemia

Question 6

Investigations for heart block

Answer 6

ECG: diagnosis
- First Degree: PR prolongation
- Second degree:
- - Mobitz I: Progressive PR prolongation until absent QRS
- - Mobitz II: No PR prolongation, random absent QRS (may be in 2:1 ratio)
- Third degree/complete: Complete dissociation between P and QRS

Troponin: ?IHD
U&Es: ?hyperkalaemia
Bone profile: ?hypercalcaemia
VBG: ?acid-base derangement
Digitalis level: ?digoxin toxicity

CXR: ?causes e.g. sarcoid, calcification
Echo: ?cause
Implantable loop recording: ecidence of block
Cardiac stress testing: ?ischaemia

Question 7

Management for first degree heart block

Answer 7

Monitoring for symptoms + ECG
Symptomatic → CCBs and beta blockers stopped

Question 8

Management for second degree heart block

Answer 8

Condition-specific management and discontinuation of AV node-blocking drugs
Permanent pacemaker (PPM) or cardiac resynchronisation therapy ± ICD placement
- AV block: dual-chamber pacemaker is placed (2” incision in dominant shoulder and place right atrial lead and right ventricular lead through subclavian vein and place pulse generator in small subcutaneous block)
- Left ventricular ejection fraction < 35% Biventricular pacemaker +/- ICD

Question 9

Management for complete heart block

Answer 9

Resolves within a few days
Insert pacemaker
If ventricular rate significantly low (<40bpm) or low BP (MABP<65mmHg) → Temporary pacing
Permanent pacemaker (PPM) or cardiac resynchronisation therapy ± ICD placement

Question 10

Complications of pacemakers

Answer 10

Bleeding
Infection
Vascular trauma
Pneumothorax
Cardiac tamponade
Lead dislodgement
Pocket haematoma

Stroke, MI, death <1%

Question 11

Prognosis of heart block

Answer 11

underlying condition strongly determines prognosis
Permanent pacing improves survival in 3rd degree heart block, especially if syncope has occurred

PPM inserted: These patients have an excellent prognosis, with a low rate of complications related to the pacemaker.