AV conduction blocks

Question 1

what drugs can cause a first degree heart block

Answer 1

beta blockers
calcium channel blockers
digoxin

Question 2

what do you see on ECG of a 1st degree HB

Answer 2

constant prolonged PR interval

Question 3

give the causes of 1st degree HB

Answer 3

• idiopathic degeneration of the conduction system
• increased vagal tone (eg. atheltes, during sleep)
• myocardial ischaemia
• drugs

Question 4

how does 1st degree HB usually present

Answer 4

asymptomatic

Question 5

what is an AV conduction block

Answer 5

a disturbance in impulse conduction between atria and ventricles

Question 6

how do you manage 1st degree HB

Answer 6

nothing - benign condition

Question 7

what is Mobitz type 1

Answer 7

intermittent failure of AV conduction resulting in occasional dropped beats

Question 8

how does Mobitz type 1 usually present

Answer 8

usually asymptomatic

may present with light headedness, dizziness, syncope, exertional fatigue

Question 9

what is a normal PR interval

Answer 9

120-200ms (3-5 small squares)

Question 10

what do you see on ECG of Mobitz type 1

Answer 10

progressive prolongation of the PR interval until a beat is dropped

Question 11

what are some causes of Mobitz type 1

Answer 11

• idiopathic degeneration
• increased vagal tone eg. athletes, during sleep
• drugs (beta blockers, calcium channel blockers, digoxin, procarinamide)
• other (TAVI, inferior MI)

Question 12

how do you manage Mobitz type 1

Answer 12

treatment not usually indicated unless symptomatic

IV atropine in emergencies

Permanent pacemaker implantation in patients w/ non resolving heart block

Question 13

what is Mobitz type II

Answer 13

an AV conduction deficit resulting in intermittent dropped beats without changes in PR interval

Question 14

what does the P wave represent

Answer 14

depolarisation of the atria and also corresponds with atrial contraction

Question 15

what are the causes of Mobitz type 11

Answer 15

idiopathic fibrosis
anterior MI

(also drugs:BBs, CCBs, digoxin, infiltrative disease)

Question 16

where does the conduction block come from in Mobitz type II

Answer 16

his bundles or purkinje fibres

Question 17

how does Mobitz type II present

Answer 17

dizziness and syncope

may present with haemodynamic instability and sudden cardiac death

Question 18

what would you see on ECG of mobitz type II

Answer 18

constant PR interval, QRS complexes may be broad if block is in the purkinje fibres

Question 19

how do you manage haemodynamic compromise is mobitz type 2

Answer 19

IV atropine
IV adrenaline
IV isoprenaline for patients with profound bradycardia
temporaroy external pacing
temporary transvenous pacing

Question 20

what is indicated for all patients with mobitz type 2

Answer 20

permanent pacemaker implantation

Question 21

what is complete heart block

Answer 21

complete failure of AV conduction, loss of communication between atria and ventricles causing them to beat independently. In worst case scenario, ventricles may come to a standstill.

Question 22

what is the most common cause of complete heart block

Answer 22

anterior or inferior MI

Question 23

what are some less common causes of complete heart block

Answer 23

idiopathic degeneration
drugs (BB, CCB, digoxin)
congenital
iatrogenic

Question 24

what are the clinical features of complete heart block

Answer 24

palpitations
symptoms of low CO - dizziness, breathlessness, fatigue

stokes-adams - episodes of syncope characterised by sudden unexpected collapse, accompanied by transient LOC

Question 25

what might you see on the JVP of patient with complete heart block

Answer 25

canon A waves

Question 26

what would you see on ECG of complete heart block

Answer 26

constant R-R and P-P intervals

QRS complexes may be narrow or wide

Question 27

how do you manage complete heart block

Answer 27

treat reversible causes

IV atropine or isoprenaline

Permanent pacemaker implantation for all patients