AV conduction blocks Flashcards
what drugs can cause a first degree heart block
beta blockers
calcium channel blockers
digoxin
what do you see on ECG of a 1st degree HB
constant prolonged PR interval
give the causes of 1st degree HB
- idiopathic degeneration of the conduction system
- increased vagal tone (eg. atheltes, during sleep)
- myocardial ischaemia
- drugs
how does 1st degree HB usually present
asymptomatic
what is an AV conduction block
a disturbance in impulse conduction between atria and ventricles
how do you manage 1st degree HB
nothing - benign condition
what is Mobitz type 1
intermittent failure of AV conduction resulting in occasional dropped beats
how does Mobitz type 1 usually present
usually asymptomatic
may present with light headedness, dizziness, syncope, exertional fatigue
what is a normal PR interval
120-200ms (3-5 small squares)
what do you see on ECG of Mobitz type 1
progressive prolongation of the PR interval until a beat is dropped
what are some causes of Mobitz type 1
- idiopathic degeneration
- increased vagal tone eg. athletes, during sleep
- drugs (beta blockers, calcium channel blockers, digoxin, procarinamide)
- other (TAVI, inferior MI)
how do you manage Mobitz type 1
treatment not usually indicated unless symptomatic
IV atropine in emergencies
Permanent pacemaker implantation in patients w/ non resolving heart block
what is Mobitz type II
an AV conduction deficit resulting in intermittent dropped beats without changes in PR interval
what does the P wave represent
depolarisation of the atria and also corresponds with atrial contraction
what are the causes of Mobitz type 11
idiopathic fibrosis
anterior MI
(also drugs:BBs, CCBs, digoxin, infiltrative disease)
where does the conduction block come from in Mobitz type II
his bundles or purkinje fibres
how does Mobitz type II present
dizziness and syncope
may present with haemodynamic instability and sudden cardiac death
what would you see on ECG of mobitz type II
constant PR interval, QRS complexes may be broad if block is in the purkinje fibres
how do you manage haemodynamic compromise is mobitz type 2
IV atropine IV adrenaline IV isoprenaline for patients with profound bradycardia temporaroy external pacing temporary transvenous pacing
what is indicated for all patients with mobitz type 2
permanent pacemaker implantation
what is complete heart block
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.
what is the most common cause of complete heart block
anterior or inferior MI
what are some less common causes of complete heart block
idiopathic degeneration
drugs (BB, CCB, digoxin)
congenital
iatrogenic
what are the clinical features of complete heart block
palpitations
symptoms of low CO - dizziness, breathlessness, fatigue
stokes-adams - episodes of syncope characterised by sudden unexpected collapse, accompanied by transient LOC
what might you see on the JVP of patient with complete heart block
canon A waves
what would you see on ECG of complete heart block
constant R-R and P-P intervals
QRS complexes may be narrow or wide
how do you manage complete heart block
treat reversible causes
IV atropine or isoprenaline
Permanent pacemaker implantation for all patients
