Heart block

Question 1

Define heart block

1st Degree AV Block:

Answer 1

prolonged conduction through the AV node

Question 2

2nd Degree AV Block:

Mobitz Type I (Wenckebach):

Answer 2

progressive prolongation of AV node conduction culminating in one atrial impulse failing to be conducted through the AV node. The cycle ten begins again.

Question 3

2nd Degree AV Block:

Mobitz Type II:

Answer 3

intermittent or regular failure of conduction through the AV node. Also defined by the number of normal conductions per failed or abnormal one (e.g. 2:1 or 3:1)

Question 4

3rd Degree (Complete) AV Block

Answer 4

no relationship between atrial and ventricular contraction. Failure of conduction through the AV node leads to ventricular contraction generated by a focus of depolarisation within the ventricle

Question 5

Summarise the epidemiology of heart block

Answer 5

250,000 pacemakers are implanted every year and they are mostly for heart block

Question 6

Explain the aetiology/risk factors of heart block

Answer 6

MI or ischaemic heart disease (MOST COMMON)

Infection (e.g. rheumatic fever, infective endocarditis)

Drugs (e.g. digoxin)

Metabolic (e.g. hyperkalaemia)

Infiltration of conducting system (e.g. sarcoidosis)

Degeneration of the conducting system

Question 7

Recognise the presenting symptoms of heart block

Answer 7

1st Degree - asymptomatic

2nd Degree - usually asymptomatic

Mobitz Type II and 3rd Degree - may cause Stokes-Adams Attacks (syncope caused by ventricular asystole)

May also cause dizziness, palpitations, chest pain and heart failure

Question 8

Recognise the signs of heart block on physical examination

Answer 8

Often NORMAL

Check for signs of a potential cause of heart block

Question 9

Recognise the signs of heart block on physical examination:

Complete Heart Block

Answer 9

Slow large volume pulse

JVP may show cannon a waves

Cannon A Waves: waves seen occasionally in the jugular vein of humans with certain cardiac arrhythmias. This occurs when the atria and ventricles contract simultaneously

Question 10

Recognise the signs of heart block on physical examination:

Mobitz Type II and 3rd Degree Heart Block

Answer 10

Signs of reduced cardiac output (e.g. hypotension, heart failure)

Question 11

Identify appropriate investigations for heart block

Answer 11

ECG - GOLD STANDARD

CXR

Bloods

Echocardiogram

Question 12

ECG - GOLD STANDARD

Answer 12

First Degree - fixed prolonged PR interval (> 0.2 s)

Mobitz Type I (Wenckebach) - progressively prolonged PR interval, culminating in a P wave that is NOT followed by a QRS complex. The pattern then begins again. ‘Going, going, gone’.

Mobitz Type II - intermittently a P wave is NOT followed by a QRS. There may be a regular pattern of P waves not followed by QRS (e.g. 2:1 or 3:1)

Complete Heart Block - no relationship between P waves and QRS complexes. If QRS is initiated in the:

Bundle of His - narrow complex

More distally - wide complex and slow rate (~ 30 bpm)

Question 13

CXR

Answer 13

Cardiac enlargement

Pulmonary oedema

Question 14

Bloods

Answer 14

TFTs

Digoxin level

Cardiac enzymes

Troponin

Question 15

Echocardiogram

Answer 15

Wall motion abnormalities

Aortic valve disease

Vegetations

Question 16

Generate a management plan for Chronic Block

Answer 16

Permanent pacemaker is recommended in:

Complete heart block

Advanced Mobitz Type II

Symptomatic Mobitz Type I

Question 17

Generate a management plan for Acute Block

Answer 17

If associated with clinical deterioration use IV atropine

Consider temporary (external) pacemaker

Question 18

Identify the possible complications of heart block

Answer 18

Asystole

Cardiac arrest

Heart failure

Complications of any pacemaker inserted

Question 19

Summarise the prognosis for patients with heart block

Answer 19

Mobitz Type II and 3rd degree block usually indicate serious underlying cardiac disease