atrial fibrillation (AF) Flashcards
define AF
arrhythmia (disrupted rhythm of cardiac beat) originating from atrial tissue
common type of supraventricular arrhythmia - above ventricle - atria
always associated with irregular heartbeat - leads to disruption of circulation around the body
describe a normal impulse
1) generated by SA node
2) propagated through atrial tissue
3) reaches AV node
4) travels through AV node slowly
5) travels through bundle of his
6) conducted simultaneously down 3 bundle branches
7) distributed through ventricular tissue by embedded purkinje fibres
describe an impulse in atrial fibrillation
1) impulse generated in atrial tissues, SAN and other focal activation, through reentry pathways instead of passing down AVN and bundle of His
2) bombards AVN in rapid + chaotic fashion
3) results in irregular heartbeat + tachycardia
why does AF lead to rhythm abnormality
disorganised electrical impulses in atria - cause atria to fibrillate at a rate of 300-600bpm
some impulses pass from AVN to ventricles - contract in an irregular manner
loss of coordination b/w atria & ventricles - leads to irregular contractions
less blood filled in atria - leads to reduced CO - risk of cardiac failure
risk factors of AF
male gender
family history
alcohol
caffeine
sepsis
hyperthyroidism
hypertension
congenital heart disease
HF
ischaemic heart diseases
symptoms of AF
could be asymptomatic
palpitations
dyspnoea - SOB
fatigue
chest discomfort
dizziness
classification of AF
paroxysmal - recurrent from 48hours - 7 days, can revert back to sinus rhythm (normal) by itself
persistent - recurrent > 7 days, can revert back to sinus with medical intervention
permanent - longstanding - cannot revert back to sinus
AF - progressive disease from paroxysmal to permanent
diagnosis of AF
normal ecg - p, qrs and t waves
AF ecg- no p wave, very irregular rhythm
rate may be fast or slow depending on rate of AVN conduction
confirmed by ECG or ILR - implantable loop recorder
what are the further investigation tests?
if they have other conditions or comorbidities that are causing AF e.g. HF or hyperthyroidism or sepsis
echocardiogram
chest X-ray
thyroid function tests
blood tests - FBC etc.
explain the pharmacological management of AF
rate vs rhythm control:
- always prefer rate control first
rate control to slow down ventricular rhythm to improve symptoms reduce O2 demand - supply mismatch - increase CO
drugs such beta blockers, CCB - titrate up until resting HR is <80bpm in symptomatic patients or more lenient <110bpm in asymptomatic patients
rhythm control:
- shock heart electrically or control rhythm pharmacologically to restore sinus rhythm
- pharmacological approach - anti-arrhythmic class 1 or 3 drugs
- direct current cardiovertion
- catheter ablation
rate control strategy - guidelines
1st line offer a BB or rate-limiting CCB unless person is sedentary or cannot use rate-limiting options
2nd - digoxin for people who are sedentary
can use digoxin with BB or CCB
amiodarone has rate controlling properties but don’t use for long-term rate control
if patient is still symptomatic - rhythm control
avoid BB, CCB, digoxin in wolff-Parkinson-white syndrome
cardioversion in AF
if patient has acute condition e.g. HF or is still symptomatic after rate-control - need cardioversion
can either cardiovert electrically or pharmacologically - DCC or amiodarone
but if using rhythm control - need to make sure their risk of stroke is very low
- absence of atrial thrombi needs to be ensured
- because thrombi present + cardioversion = 91% stroke rate
- in left atrium - there is an opening - if cardiovert - high risk that clot will go from heart to brain
- so need to use anticoagulant
Rhythm control strategy for persistent AF
persistent AF - duration >48hrs
if not on anticoagulants
- then give anticoagulation for 3 weeks before cardioversion
if already on anticoagulants
- risk of stroke already low so can do cardioversion or amiodarone therapy - electrical or pharmacological
rhythm control strategy for paroxysmal AF
paroxysmal AF:
offer BB - rate control
pill in the pocket strategy - no drug treatment as paroxysmal will go back to normal
for patients with HF or Left ventricular impairment
- can only give amiodarone
- do not give class 1c anti-arrhythmic drugs to people with heart disease
if rhythm control treatment fails - ablation strategy
describe rhythm control pharmacotherapy?
3 weeks anti coagulation before starting these:
class III anti-arrhythmic amiodarone - safe in patients with structural heart disease, HF
class 1c anti-arrhythmic flecainide, c/i in patients with structural heart disease
other rhythm control drugs:
soltalol - BB with anti-arrhythmic properties
dronaderone - c/i in patients with HF
what is catheter ablation?
catheter ablation - used for treatment of irregular heartbeats called arrhythmias
uses heat or cold energy to create tiny scars in the heart
these tiny scars block faulty heart signals - restoring typical heartbeat - sinus rhythm
what is the link b/w AF and stroke?
it is important regardless of rate or rhythm control to assess every patient that has AF for risk of stroke
- approximately 1in5 stroke patients have AF as underlying score - often fatal
AF - inadequate blood flow to areas of heart - blood clot
blood clots can dislodge and travel to brain - result in stroke
what assessments need to be done for stroke prevention and anticoagulation in AF patients?
chadvasc score - assesses risk of stroke in AF patients
ORBIT bleeding score - assesses potential risk of bleeding in patients on anticoagulants
need to weigh up these and decide with patient if anticoagulant will be given or not
most of the time - stroke risk outweighs bleeding risk as stroke is more fatal
guidelines for giving anticoagulation
if chadvasc score > or equal to 2 - give anticoagulant
if chadvasc score = 1 in men - give anticoagulant
if chadvasc score < or equal 1 in women and =0 in men - do not give anticoagulant
what are the anticoagulant drug options
1st line - DOAC - direct acting anticoagulant e.g. rivoroxaban, edoxaban
- if c/i or patients already on warfarin switch to warfarin
- take into account TTR - time in therapeutic range
- therapeutic range - 2-3 times
vitamin K antagonist - warfarin
- calculate TTR at each visit
- number of INR within therapeutic range over total number x 100
- tells you if patient is poorly controlled on warfarin - consider switching to DOAC
- poorly controlled - 2 INR values >5, 1INR value > 8 or TTR <65%
what do you do if patient is at a high risk of stroke and high risk of bleeding or c/i to anticoagulation (DOACs & warfarin)
left atrial appendage occlusion
- non pharmacological way of removing clot if cant use anticoagulant
- small ear shaped sac in muscle wall of left atrium called LAA
- in AF - atria can’t effectively squeeze blood from atria to ventricle - can collect in LAA and cause clot - when clot is pumped out can cause stroke
- process is safe and effective
- stent blocks the pouch so clot cannot form
common anticoagulation counselling
alert patients to report bleeding or bruising
explain dosage and monitoring
drug interactions
OTC medicines
alert cards/booklets
summary of AF
irregular cardiac arrhythmias
risk of stroke - fatal
rate control and rhythm control
anticoagulation assessment
treatment aims to reduce symptoms and prevent stroke
