Transcript Atrial fibrillation (11-01-12)

Atrial fibrillation
What is it?

AF is an arrhythmia is which electrical activity in the atria is
disorganised
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The AV node receives more electrical impulses than it can
conduct, and many are blocked, resulting in an irregular
ventricular rhythm
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If untreated the ventricular rate averages 160-180bpm (or
even lower)
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AF is the most common arrhythmia in clinical practice
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Prevalence doubles with each advancing decade from the
age of 50 years
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AF doubles mortality rate
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Stroke risk is increased 6x and in AF with rheumatic heart
disease 18x
What causes it?
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Most common
 IHD, Hypertension, Mitral stenosis, Hyperthyroidism
Cardiac &/or valve conditions
 Heart failure, rheumatic heart disease, pre-excitation
syndromes (eg Wolff Parkinson White syndrome)
Non cardiac conditions
 Lung cancer, acute infections
Dietary and lifestyle factors
 Excess alcohol, excess caffeine, obesity
How might AF present in GP?
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People with an irregular pulse +/ Asymptomatic
 Palpitations
 Chest pains
 Breathlessness
 Syncope / giddiness
 Reduced exercise tolerance, malaise or polyuria
 A potential complication of AF such as stroke, TIA or
heart failure
Diagnosis
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Manual pulse palpation very sensitive but specificity less good
ECG
 No P waves
 Chaotic baseline
 Irregular ventricular rate
 Ventricular complexes look normal unless there is a conduction
defect
If paroxysmal AF suspected AF and 12 lead ECG is normal then
arrange ambulatory ECG
Bloods
CXR
Bloods?
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FBC – exclude anaemia
U+Es, bone profile, glucose – exclude electrolyte
disturbances which may precipitate AF
LFTs and clotting – suitability for warfarin
CXR – lung cancer, detect heart failure
When to urgently refer
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Pulse >150bpm &/or low BP (systolic < 90 mmHg)
Loss of consciousness, severe dizziness, ongoing chest pain
or increasing breathlessness
Complication of AF
 Stroke, TIA, acute HF
Key priority ― Detection and diagnosis
NICE clinical guideline 36, June 2006
Case
detection
Assessment
O
R
Ratecontrol
Rhythmcontrol
Follow-up
Follow-up
Referral
An ECG should be
performed in all patients,
whether symptomatic or
not, in whom AF is
suspected because an
irregular pulse has been
detected
Classification
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Paroxysmal
 Intermittent and recurrent, but terminates
spontaneously (35-65% of all cases)
 Reverts to sinus rhythm within 7 days
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Persistent
 Does not convert spontaneously, but may be converted
electrically or by the use of drugs
 Lasts over 7 days and less than a year
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Permanent
 Long standing and resistant to cardioversion. Also term
for long-standing AF (>1year) where cardioversion has
not been attempted
Complications
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Stroke and thromboembolic events
 6x greater risk
Heart failure
Tachycardia-induced cardiomyopathy
Critical cardiac ischaemia
Poorer life quality
Prognosis
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Mortality from AF up to 2x general population
 Linked to severity of underlying heart disease (eg heart
failure, cardiomyopathy or myocardial ischaemia)
Acute onset AF
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Requires immediate hospitalisation and urgent intervention
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Those at highest risk include:
 Ventricular rate >150bpm
 Ongoing chest pain
 Critical ischaemia
Treatment options
Antithrombotic
therapy
Treatment options – antithrombotic therapy
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Warfarin is more effective but balance this against a higher
risk of a major bleed
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Warfarin reduces relative risk of all strokes vs placebo by
60%
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Aspirin reduces relative risk of all strokes vs placebo by
20%
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Actual benefit is based on persons baseline risk
Key priority ― Assess for risk of stroke &
thromboembolism
NICE clinical guideline 36, June 2006
Case
detection
Assessment
O
R
Ratecontrol
Rhythmcontrol
Follow-up
Follow-up
Referral
- Use the stroke risk
Stratification algorithm
to assess risk
- Use antithrombotic
therapy as appropriate
- Initiate antithrombotic
therapy without minimal
delay in patients newly
diagnosed with AF
Assess for risk of stroke and thromboembolism
NICE clinical guideline 36, June 2006
Determine stroke/thromboembolic risk
High risk:
• Previous
ischaemic
stroke/TIA or
thromboembolic
event
• Age >75 with
hypertension,
diabetes or
vascular disease
• Clinical evidence
of valve disease,
heart failure, or
impaired left
ventricular function
on
echocardiography
Moderate
risk:
Low risk:
• Age >65 with
no moderate or
high risk factors
no high risk
factors
• Age <75 with
hypertension,
diabetes or
vascular
disease
• Age <65 with
Patients with AF
NICE clinical guideline 36, June 2006
Determine stroke/thromboembolic risk
High
risk
Consider anticoagulation
Contraindications to
warfarin?
NO
Warfarin, target INR = 2.5
(range 2.0 to 3.0)
Moderate
risk
Low
risk
Consider anticoagulation
or aspirin
Aspirin 75 to 300 mg/day
if no contraindications
YES
Reassess risk stratification
whenever individual risk
factors are reviewed
CHADS2
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Congestive heart failure = 1
Hypertension (or treated hypertension) = 1
Age older than 75 years = 1
Diabetes mellitus = 1
Previous Stroke or TIA = 2
Treat with aspirin if total score is 0 or 1
Use warfarin if score is 2 or more
Possible questions?
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How do the harms and benefits of aspirin compare?
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How does low dose warfarin compare with adjusted dosing?
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What about using clopidogrel instead of aspirin?
How do the harms and
benefits of aspirin
compare?
Harms from aspirin
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Take 1000 patients
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6 will have a major extracranial bleeding in 1 year anyway
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If they take aspirin 1 more will have a bleed caused by
aspirin
Harms from warfarin
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Take 1000 patients
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6 will have a major extracranial bleeding in 1 year anyway
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If they take warfarin 3 more will have a bleed caused by
warfarin
Anticoagulation
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Assessment of bleeding risk should be part of clinical
assessment prior to starting anticoagulation
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Benefits and potential risks of anticoagulation should be
discussed
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Aim for INR between 2 and 3
Benefits of aspirin
(low risk eg 1% per year)
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Take 1000 patients
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10 will have a stroke in 1 year (1%)
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If aspirin is taken 8 will have a stroke
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2 will be prevented from having a stroke
Benefits of warfarin
(low risk eg 1% per year)
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Take 1000 patients
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10 will have a stroke in 1 year (1%)
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If warfarin is taken 4 will have a stroke
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6 will be prevented from having a stroke
Benefits of aspirin
(moderate risk eg 3.5% per year)
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Take 1000 patients
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35 will have a stroke in 1 year (3.5%)
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If aspirin is taken 28 will have a stroke
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7 will be prevented from having a stroke
Benefits of warfarin
(moderate risk eg 3.5% per year)
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Take 1000 patients
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35 will have a stroke in 1 year (3.5%)
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If warfarin is taken 14 will have a stroke
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21 will be prevented from having a stroke
Benefits of aspirin
(higher risk eg 6% per year)
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Take 1000 patients
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60 will have a stroke in 1 year (6%)
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If aspirin is taken 48 will have a stroke
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12 will be prevented from having a stroke
Benefits of warfarin
(higher risk eg 6% per year)
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Take 1000 patients
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60 will have a stroke in 1 year (6%)
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If warfarin is taken 24 will have a stroke
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36 will be prevented from having a stroke
How does low dose warfarin
compare with adjusted
dosing?
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Adjusted dosing is better with no obvious increased harms
What about using clopidogrel
instead of aspirin?
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No evidence of significant benefit
Clopidogrel alone (within its unlicensed indications) is
recommended for people who are intolerant of low dose
aspirin and either have:
 Experienced an occlusive vascular event
 Have symptomatic PAD
Aspirin intolerance is either:
 Proven hypersensitivity to aspirin containing medicines
 History of severe dyspepsia induced by low dose aspirin
Treatment options
Rate or rhythm
control
Treatment for persistent AF
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2 treatment options
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Rate control involves the use of chronotropic drugs or
electrophysiological / surgical interventions
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Rhythm control involves the use of electrical or
pharmacological cardioversion for persistent AF, or
suppression of recurrent (eg paroxysmal) AF
There is a need for appropriate antithrombotic therapy if
rhythm control is chosen
NICE clinical guideline 36, June 2006. Quick Reference Guide
Treatment for paroxysmal AF
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Patients can be highly symptomatic
3 main aims of Rx are to :
 Suppress paroxysms of AF and maintain sinus rhythm
 Control heart rate during paroxysms of AF
 Prevent complications
Treatment strategies include out of hospital initiation of
antiarrhythmic drugs : ‘pill in the pocket’ approach
Patients with paroxysmal AF carry the same risks of stroke
and thromboembolism as those with persistent AF
Key priority ― choosing the most effective treatment
NICE clinical guideline 36, June 2006
Case
detection
Assessment
O
R
Ratecontrol
Rhythmcontrol
Follow-up
Follow-up
Referral
-Some patients with
persistent AF will satisfy
criteria for either an initial
rate or rhythm control strategy
-Indications for each Rx are
not mutually exclusive
-Involve the patient in the
treatment decision
-Take comorbidities into
account
-Antithrombotic therapy
should always be used
Rate control
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What is it?
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Control the ventricular rate (AF remains)
How is it done?
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Drugs that block AV node conduction (B blockers, Ca channel blockers, digoxin)
Why is it done?
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Reduce symptoms and myopathy
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Prevention of embolism & cardiomyopathy
Advantages?
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As effective as rhythm control
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Lower risk of adverse events
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Lower cost
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Less hospitalisation
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Avoids antiarrhythmics
Disadvantages?
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May not remove symptoms
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Requires anticoagulation
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Risk of tachycardiomyopathy
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Atrial remodelling (permanent)
When may it be appropriate?
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First line particularly in elderly with minimal symptoms
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Patients at high risk of stroke
Rate control strategy
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Try rate control 1st for patients with persistent AF :
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Over 65
With CHD
With contraindications to antiarrhythmic drugs
Unsuitable for cardioversion
Without CCF
Rhythm control
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What is it?
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Restore and maintain sinus rhythm
How is it done?
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Electrical / drug conversion (plus maintenance antiarrhythmic drugs)
Why is it done?
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Reduce symptoms and myopathy
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Prevention of embolism & cardiomyopathy
Advantages?
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Better exercise tolerance
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Improved haemodynamic function
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Reverse modelling?
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Less need for, but still requires, antithrombotic treatment
Disadvantages?
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Difficult to maintain in long term
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High adverse event rate
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More hospitalisation
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High rates of recurrence
When may it be appropriate
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Young patients
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New onset AF
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Where rate control ineffective or symptoms remain
Rhythm control strategy
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Try rhythm control 1st for patients with persistent AF :
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Who are symptomatic
Who are younger
Presenting for the 1st time with lone AF
Secondary to a treated / corrected precipitant
With CCF
What about restoring sinus rhythm?
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DC cardioversion restores sinus rhythm in >80%
In AF of recent onset drugs have a success rate of 40-90%
Sinus rhythm at 1y is maintained in 30% without
antiarrhythmic therapy but in 50% with such therapy
Follow up and referral
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Follow up after cardioversion should be at 1 month and
then tailored to the individual
Reassess the need for anticoagulation at each review
Referral for further specialist intervention should be
considered in those :
 In whom pharmacological therapy has failed
 With lone AF
 With ECG evidence of any underlying
electrophysiological disorder