Heart Block

Question 1

Define 1st Degree AV Block?

Answer 1

Prolonged conduction through the AV node

Question 2

Define Mobitz Type 1 (Wenckebach) 2nd Degree AV Block?

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

Define Mobitz Type II 2nd Degree AV Block?

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

Define 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

What is the epidemiology of Heart Block?

Answer 5

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

Question 6

What is the aetiology and 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

What are the presenting symptoms of 1st Degree Heart Block?

Answer 7

Asymptomatic

Question 8

What are the presenting symptoms of 2nd Degree Heart Block?

Answer 8

Usually asymptomatic

Question 9

What are the presenting symptoms of Mobitz Type II and 3rd Degree Heart Block?

Answer 9

Stokes-Adams Attacks 
Dizziness 
Palpitations
Chest Pain
Heart Failure

Question 10

What are the signs of heart block on physical examination?

Answer 10

Often NORMAL

Check for signs of a potential cause of heart block

Question 11

What are the signs of Complete Heart Block?

Answer 11

Slow large volume pulse

JVP may show cannon a waves

Question 12

What are Stokes-Adams Attacks?

Answer 12

Syncope caused by ventricular asystole

Question 13

What are Cannon A waves?

Answer 13

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

Question 14

What are the signs of Mobitz Type II and 3rd Degree Heart Block?

Answer 14

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

Question 15

What is the gold standard investigation for heart block?

Answer 15

ECG

Question 16

What might you see on an ECG for First Degree Heart Block?

Answer 16

Fixed prolonged PR interval (> 0.2s)

Question 17

What might you see on an ECG for Mobitz Type I Heart Block?

Answer 17

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’

Question 18

What might you see on an ECG for Mobitz Type II Heart Block?

Answer 18

Intermittently a P wave is not followed by a QRS

There may be a regular pattern of P waves not followed by QRS

Question 19

What might you see on an ECG for Complete Heart Block?

Answer 19

No Relationship between P waves and QRS complexes
If QRS is initated in the Bundle of His - narrow complex
More Distally - wide complex and slow rate (roughly 30bpm)

Question 20

What might we see on a CXR for heart block?

Answer 20

Cardiac Enlargement

Pulmonary oedema

Question 21

What bloods would we do for Heart Block?

Answer 21

TFTs
Digoxin Level
Cardiac Enzymes
Troponin

Question 22

What might we see on an Echocardiogram for Heart Block?

Answer 22

Wall motion abnormalities
Aortic Valve Disease
Vegetations

Question 23

What management plan would we do for Chronic Heart Block?

Answer 23

Permanent pacemaker is recommended in:

• Complete Heart Block
• Advanced Mobitz Type II
• Symptomatic Mobitz Type I

Question 24

What management plan would we do for Acute Heart Block?

Answer 24

If associated with clinical deterioration use IV atropine
Consider temporary (external) pacemaker

Question 25

What are some complications of Heart Block?

Answer 25

Asystole
Cardiac Arrest
Heart Failure
Complications of any pacemakers inserted

Question 26

What is the prognosis for patients with Heart Block?

Answer 26

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