Heart Block

Question 1

What is another name for atrioventricular block?

Answer 1

Heart block

Question 2

What is heart block?

Answer 2

It is when there is impaired electrical conduction between the atria and ventricles

Question 3

What are the three types of heart block?

Answer 3

1st degree

2nd degree

3rd degree

Question 4

What is first degree heart block?

Answer 4

This is when there is delayed AV conduction through the AV node

Question 5

What is a sign of first degree heart block on ECGs?

Answer 5

PR interval > 0.2s

Question 6

How do we manage first degree heart block?

Answer 6

It is usually asymptomatic and doesn’t require treatment

Question 7

What is second degree heart block?

Answer 7

This is where some of the atrial impulses don’t make it through the AV node to the ventricle

This means that there are instances where P waves don’t lead to QRS complexes

Question 8

What are the two subtypes of second degree heart block?

Answer 8

Mobitz type I

Mobitz type II

Question 9

What is another term for Mobitz type I?

Answer 9

Wenckebach’s phenomenon

Question 10

What is Mobitz type I?

Answer 10

This is where the atrial impulses becomes gradually weaker until it does not pass through the AV node

After failing to stimulate a ventricular contraction the atrial impulse returns to being strong

This cycle then repeats

Question 11

How does Mobitz 1 present on ECG scan?

Answer 11

Increasing PR interval until the P wave no longer conducts to ventricles

An absent QRS complex after a P wave

The PR interval then returns to normal but progressively becomes longer again until another QRS complex is missed

This cycle repeats itself

Question 12

What is Mobitz type II?

Answer 12

This is is where there is intermittent failure or interruption of AV conduction

This results in missing QRS complexes

The PR interval remains constant; however, the P wave is not often followed by a QRS complex

Question 13

What is a 3:1 Mobitz type II heart block?

Answer 13

There are three P waves to each QRS complex

Question 14

What is another term for third degree heart block?

Answer 14

Complete heart block

Question 15

What is third degree heart block?

Answer 15

This is where there no impulses are passed from the atria to the ventricles

This means that there is no association between the P waves and QRS complexes

Question 16

Which artery is usually affected in complete heart block?

Answer 16

Right coronary artery

Question 17

In which two heart blocks is there a risk of astolye?

Answer 17

Second degree Mobitz type II

Third degree heart block

Question 18

What are the five clinical features of heart block?

Answer 18

Syncope

Bradycardia (30 – 50bpm)

Wide Pulse Pressure

JVP Cannon Waves

Variable Intensity of S1

Question 19

What is the first line management option for heart block?

Answer 19

Atropine

Question 20

What is the mechanism of action for atropine?

Answer 20

This is an antimuscarinic medication and works by inhibiting the parasympathetic nervous system

Question 21

What dose of atropine is initially administered?

Answer 21

500mcg IV

Question 22

What do we do if the initial dose of atropine doesn’t make any improvement?

Answer 22

We can repeat up to 6 doses for a total of 3mg

Question 23

What is the second line management option for heart block?

Answer 23

Inotropes

Question 24

What inotrope agent can be administered to treat heart block?

Answer 24

Noradrenaline

Question 25

What is the third line management option for heart block?

Answer 25

Transcutaneous cardiac pacing

Question 26

What is transcutaneous cardiac pacing?

Answer 26

This involves using an electrode on the end of a wire that is inserted into a vein and fed through the venous system to the right atrium or ventricle to stimulate them directly