Heart Block Flashcards
what is the general definition of heart block
impaired AV node conduction
represented by interval between P wave and QRS complex
what is the definition of first degree heart block
prolonged conduction through AV node
what are the two types of second degree heart block
mobitz t1 (wenkebach) mobitz t2
what is the definition of second degree heart block mobitz t1
irregular
progressive prolongation of AV node conduction
culminates in an atrial impulse failing to be conducted through the AV node
what is the definition of second degree heart block mobitz t2
regular
regular failure of AV node conduction
also defined by no. of normal conductions to a failed conduction
what is the definition of third degree heart block
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
what is the most common cause of heart block
MI/IHD
what is the aetiology of heart block
1 MI/IHD 2 infection (RF/IE) 3 drugs (digoxin/BBs/CCBs) 4 metabolic (hyperkalaemia) 5 infiltration (sarcoidosis)/degeneration of conduction system
what is the history associated with first degree heart block
asymptomatic
what is the history associated with second degree heart block motbitz t1
asymptomatic
what is the history associated with second degree heart block mobitz t2 and third degree heart block
Stoke-Adams attacks (syncope by ventricular asystole)
palpitations
chest pain
HF
what would be the expected examination findings in third degree heart block only
slow large volume pulse
JVP may show ‘cannon waves’
what would be the expected examination findings in both third degree heart block and second degree heart block mobitz t2
signs of reduced CO (hypotension/HF)
bradycardia
what investigations would be performed in suspected heart block
1 ECG +consider 24H Holter
2 CXR
3 blood
4 echo
what would you expect to find on an ECG with heart block
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
where else is ventricular conduction in third degree heart block intiated
Bundle of His-narrow QRS
More distally-wide and slow (30bpm)
what would you expect to find on an CXR with heart block
cardiomegaly
pulmonary oedema
what is the management for chronic heart block
permanent pacemaker in 3rd degree/advanced mobitz t2/symptomatic mobitz t1
what is the management for acute heart block (e.g. secondary to MI)
if associated with clinical deterioration
- IV atropine
- temporary pacemaker
what are the complications associated with heart block
asystole
cardiac arrest
HF
complications of pacemaker insertion
what is the prognosis of second degree mobitz t2 and third degree heart block
indicates serious underlying cardiac disease
risk factors
age-related degeneration of the conduction system
CAD
CHF
what are A waves associated with
cannon A waves may indicate complete heart blocck
reflect contraction of RA against closed tricuspid valve
what is bifascular block
combination of RBBB and LAFB (left anterior fascicular block) or LPFB (left posterior fascicular block)
what are common causes of bifascular block
IHD
HTN
