Arrhythmias- Bradycardias Flashcards
normal sinus rhythm is characterised by?
p wave preceding every QRS complex
what are arrhythmias?
abnormal heart rhythms
what are the only 3 normal heart rhythms?
- sinus rhythm
- sinus tachycardia
- sinus bradycardia
definition of bradycardias?
<60bpm
classification of bradycardias?
- sinus bradycardia
- heart block
- 1st degree
- 2nd degree
- complete
causes? mnemonic
DIVISIONS
Drugs
- anti-arrhythmics (type 1a, amiodarone)
- beta blockers
- ca channel blockers
- digoxin
Ischaemia / Infarction
Vagal hypertonia
- athletes
- vasovagal syncope
- carotid sinus syndrome
Infection
- viral myocarditis
- IE
- rheumatic fever
Sick sinus syndrome
Infiltration
- restrictive/dilated cardiomyopathy
O
- hypothyroidism
- hypokalaemia
- hypothermia
Neuro: raised ICP
Septal defect: osteum primum ASD / Surgery
what is sick sinus syndrome?
structural damage / fibrosis to SAN, AVN or conducting tissue
how does sick sinus syndrome present?
SVT alternating with either sinus bradycardia +/- arrest or SA/AV node block
outline the classification of heart block
- 1st degree
- 2nd degree
- mobitz type I
- mobitz type II
- 3rd degree
pathology of heart block?
damage to SA/AV node or His/Purkinje fibres
symptoms of heart block?
syncope, SOB, HF
pathology of 1st degree?
- delayed AV conduction through AV node
- every atrial impulse leads to ventricular contraction (every P wave = QRS complex)
- PR interval >0.2seconds
what happens in 2nd degree?
some of the atrial impulses do not make it through to the ventricles
pathology of Mobitz type I?
- PR interval gradually increases in length until there is a missed beat
- after failing to stimulate ventricular contraction, atrial impulse returns to being strong & cycle repeats
pathology of Mobitz type II?
- interruption of AV conduction- results in missing QRS complexes
- PR interval remains normal
- risk of asystole
- usually set ratio of p waves to QRS (if it’s 3 it’s called 3:1 block)
pathology of 3rd degree?
- complete heart block - no observable relationship between p waves & QRS
- significant risk of asystole
Rx?
- Stable–> observe
- Unstable/risk of asystole
- Atropine 500mcg IV
if there is no improvement w atropine?
- atropine 500mcg IV again (can give up to 6 doses- max 3mg)
- other inotropes ie noradrenaline
- transcutaenous cardiac pacing ie defib
- any pts w symptomatic 2nd/3rd degree heart block should have this
Rx in pts with high risk of asystole?
- temporary transvenous cardiac pacing
- permanent implantable pacemaker when available
what kind of drug is atropine?
antimuscarinic- inhibits PNS
