Atrial Fibrilation Flashcards
what is atrial fibrillation?
when the electrical activity of the atria becomes disorganised
causes fibrillation (random muscle twitching) of the atria
leads to an irregularly irregular pulse
what are the overall effects of atrial fibrillation?
irregularly irregular ventricular contractions
tachycardia
heart failure - due to impaired filling of ventricles during diastole
increased risk of stroke
what does the sinoatrial node normally do?
produces organised electrical activity that coordinates the contraction of the atria
what happens to the electricity in the heart in atrial fibrillation?
it becomes disorganised
the chaotic electricity overrides the normal electricity from the sinoatrial node
what does the disorganised electricity in the heart lead?
uncoordinated, rapid, irregular atrial contractions
what happens when the disorganised electricity overrides the normal electricity from the SA node?
the disorganised electricity passes to the ventricles
causing irregularly irregular ventricular contractions
what can uncoordinated atrial contractions cause blood to do?
stagnate in the atria
forming thrombus (blood clot)
what can a thrombus in the left atrium cause?
ischaemia stroke
if the blood clot travels to the brain and blocks a cerebral artery
what is the risk of stroke associated with atrial fibrillation?
patients with AF are at a 5x higher risk than usual
what are the causes of atrial fibrillation?
Sepsis
Mitral valve pathology
Ischaemic heart disease
Thyrotoxicosis
Hypertension
what are lifestyle causes of AF?
alcohol
caffeine
what are patients with AF often?
asymptomatic
when is AF commonly found?
accidentally
may be diagnosed after a stroke
how may patients with AF present?
palpitations
shortness of breath
dizziness/syncope
symptoms of associated conditions - stroke, sepsis, thyrotoxicosis
what is a key exam finding?
irregularly irregular pulse
what does an irregularly irregular pulse mean?
the patient has either atrial fibrillation or ventricular ectopics
what suggests a diagnosis of ventricular ectopics and why?
a normal heart whilst exercising
ventricular ectopics disappears once the heart rate is above a certain threshold
what do all patients with an irregularly irregular pulse require?
ECG
what are the ECG findings for atrial fibrillation?
absent P waves
narrow QRS complex tachycardia
irregularly irregular ventricular rhythm
what may an echocardiogram be used for in atrial fibrillation?
further investigations of:
valvular heart disease
heart failure
planned cardioversion
what is paroxysmal atrial fibrillation?
reoccurring episodes of atrial fibrillation that spontaneously go back to normal sinus rhytm
how long can episodes of paroxysmal atrial fibrillation last?
between 30s and 48hrs
what are patients with suspected paroxysmal atrial fibrillation and a normal ECG given for further investigation?
24hr ambulatory ECG
cardiac event recorder listing 1-2 weeks
what is valvular atrial fibrillation?
atrial fibrillation with significant mitral stenosis or a mechanical heart valve
the assumption is that the valve pathology has left to AF
what is non-valvular AF?
AF with no valvular pathology or other valvular pathology - i.e. mitral regurgitation or aortic stenosis
what are the principles of management for atrial fibrillation?
rate or rhythm control
anticoagulation - prevent strokes
how do the ventricles fill with blood when the atrial contractions are uncoordinated?
gravity and suction - much less effective
increased heart rate = less time for the ventricles to fill = decreased cardiac output
what are the aims or rate control?
to get the heart rate below 100bpm and extend the time of diastole for the ventricles to fill
who is rate control not first line for when managing atrial fibrillation?
reversible causes of AF
new onset AF - within the last 48hrs
HF caused by AF
symptoms despite effectively rate controlled
what medications are used for rate control?
beta blockers are first line - atenolol or bisoprolol
calcium channel blockers - dilimiazem or verapamil but should be avoided in those with HF
digoxin - only for sedentary people with persistent AF, needs monitoring and there is a risk of toxicity
when is rhythm control used?
when rate control is not :
reversible causes of AF
new onset AF - within last 48hrs
HF caused by AF
symptomatic despite being effectively rate controlled
what are the aims of rhythm control?
to return the heart to normal sinus rhythm
what are the two methods of rhythm control?
cardioversion
long-term rhythm control - medication
what are the two types of cardio version?
immediate
delayed
when is immediate cardoversion used?
when atrial fibrillation:
has been present for less than 48hrs
is causing life-threatening haemodynamic instability
what are the two methods of immediate cardio version?
pharmocological
electrical
what drugs can be used for pharmacological cardio version?
flecanide
amiodarone - useful for patient with structural heart disease
what is the aim of electrical cardio version?
to shock the heart back into sinus rhythm
how is electrical cardioversion done?
with a cardiac defibrillator machine that delivers a controlled shock
this is usually done under sedation or general anaesthetic
when is delayed cardioversion used?
when atrial fibrillation;
has been present for more than 48hrs and the patient is stable
what type of cardioversion is recommended for delayed cardioversion?
electrical
transoesophageal echocardiography-guided cardioversion is also an option when available
what medication may be considered before and after a delayed cardioversion and why?
amiodarone
to prevent atrial fibrillation from recurring
what should a patient be for at least 3 weeks before a cardioversion and why?
anticoagulated
within 48hrs before they may develop a thrombus
reverting to sinus rhythm has a high risk of mobilising the clot and causing a stroke
how are patients awaiting delayed cardioversion managed?
rate control
what medications can be used for long-term rhythm control?
beta blockers are first line
dronedarone is second line for maintaining sinus rhythm after a successful cardioversion
amiodarone is useful for patients with heart failure or left ventricular dysfunction
what may patients with paroxysmal atrial fibrillation be suitable for?
pill in the pocket
what is pill in the pocket?
where patients take a pill to terminate their AF but only when they feel symptoms
what is required for pill in the pocket?
infrequent episodes
no structural heart disease
identify signs of AF
understand when to take pill
what drug is usually used for pill in the pocket?
flecanide
should still be anti coagulated if qualify
what is the risk of flecanide in AF?
risk of converting atrial fibrillation into atrial flutter with 1:1 conduction to the ventricles = very fast ventricular rate
