Heart Block

Question 1

what is the general definition of heart block

Answer 1

impaired AV node conduction

represented by interval between P wave and QRS complex

Question 2

what is the definition of first degree heart block

Answer 2

prolonged conduction through AV node

Question 3

what are the two types of second degree heart block

Answer 3

mobitz t1 (wenkebach)
mobitz t2

Question 4

what is the definition of second degree heart block mobitz t1

Answer 4

irregular
progressive prolongation of AV node conduction
culminates in an atrial impulse failing to be conducted through the AV node

Question 5

what is the definition of second degree heart block mobitz t2

Answer 5

regular
regular failure of AV node conduction
also defined by no. of normal conductions to a failed conduction

Question 6

what is the definition of third degree heart block

Answer 6

no relationship between atrial and ventricular contraction
complete dissociation of P wave to QRS complex
failure of conduction through AV node leads to ventricular contraction generated by a focus of depolarisation from within the ventricle

Question 7

what is the most common cause of heart block

Answer 7

MI/IHD

Question 8

what is the aetiology of heart block

Answer 8

1 MI/IHD
2 infection (RF/IE)
3 drugs (digoxin/BBs/CCBs)
4 metabolic (hyperkalaemia)
5 infiltration (sarcoidosis)/degeneration of conduction system

Question 9

what is the history associated with first degree heart block

Answer 9

asymptomatic

Question 10

what is the history associated with second degree heart block motbitz t1

Answer 10

asymptomatic

Question 11

what is the history associated with second degree heart block mobitz t2 and third degree heart block

Answer 11

Stoke-Adams attacks (syncope by ventricular asystole)
palpitations
chest pain
HF

Question 12

what would be the expected examination findings in third degree heart block only

Answer 12

slow large volume pulse

JVP may show ‘cannon waves’

Question 13

what would be the expected examination findings in both third degree heart block and second degree heart block mobitz t2

Answer 13

signs of reduced CO (hypotension/HF)

bradycardia

Question 14

what investigations would be performed in suspected heart block

Answer 14

1 ECG +consider 24H Holter
2 CXR
3 blood
4 echo

Question 15

what would you expect to find on an ECG with heart block

Answer 15

1st degree
-prolonged PR interval (0.2s)
2nd degree mobitz 1
-irregular
-progressively prolonged PR interval
-P wave is not followed by QRS
2nd degree mobitz 2
-regular
-intermittant a P wave is not followed by QRS
3rd degree
-no relationship between P waves and QRS
-no conduction
-QRS conduction is initiated elsewhere

Question 16

where else is ventricular conduction in third degree heart block intiated

Answer 16

Bundle of His-narrow QRS

More distally-wide and slow (30bpm)

Question 17

what would you expect to find on an CXR with heart block

Answer 17

cardiomegaly

pulmonary oedema

Question 18

what is the management for chronic heart block

Answer 18

permanent pacemaker in 3rd degree/advanced mobitz t2/symptomatic mobitz t1

Question 19

what is the management for acute heart block (e.g. secondary to MI)

Answer 19

if associated with clinical deterioration

• IV atropine
• temporary pacemaker

Question 20

what are the complications associated with heart block

Answer 20

asystole
cardiac arrest
HF
complications of pacemaker insertion

Question 21

what is the prognosis of second degree mobitz t2 and third degree heart block

Answer 21

indicates serious underlying cardiac disease

Question 22

risk factors

Answer 22

age-related degeneration of the conduction system
CAD
CHF

Question 23

what are A waves associated with

Answer 23

cannon A waves may indicate complete heart blocck

reflect contraction of RA against closed tricuspid valve

Question 24

what is bifascular block

Answer 24

combination of RBBB and LAFB (left anterior fascicular block) or LPFB (left posterior fascicular block)

Question 25

what are common causes of bifascular block

Answer 25

IHD

HTN