Atrial fibrillation

What is it? AF is an arrhythmia is which electrical activity in the atria is

disorganised

The AV node receives more electrical impulses than it can conduct, and many are blocked, resulting in an irregular ventricular rhythm

If untreated the ventricular rate averages 160-180bpm (or even lower)

AF is the most common arrhythmia in clinical practice

Prevalence doubles with each advancing decade from the age of 50 years

AF doubles mortality rate

Stroke risk is increased 6x and in AF with rheumatic heart disease 18x

What causes it? 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? 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 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? 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 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

Case detection

Assessment

Rate- contro

l

Rhythm-

control

Referral

Follow-up

Follow-up

OR

Key priority ― Detection and diagnosisNICE clinical guideline 36, June 2006

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 Paroxysmal

Intermittent and recurrent, but terminates spontaneously (35-65% of all cases)

Reverts to sinus rhythm within 7 days

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

Permanent Long standing and resistant to cardioversion. Also term

for long-standing AF (>1year) where cardioversion has not been attempted

Complications Stroke and thromboembolic events

6x greater risk Heart failure Tachycardia-induced cardiomyopathy Critical cardiac ischaemia Poorer life quality

Prognosis 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 Requires immediate hospitalisation and urgent intervention

Those at highest risk include: Ventricular rate >150bpm Ongoing chest pain Critical ischaemia

Treatment options

Antithrombotic therapy

Treatment options – antithrombotic therapy Warfarin is more effective but balance this against a higher

risk of a major bleed

Warfarin reduces relative risk of all strokes vs placebo by 60%

Aspirin reduces relative risk of all strokes vs placebo by 20%

Actual benefit is based on persons baseline risk

Case detection

Assessment

Rate- contro

l

Rhythm-

control

Referral

Follow-up

Follow-up

OR

Key priority ― Assess for risk of stroke & thromboembolismNICE clinical guideline 36, June 2006

- Use the stroke riskStratification algorithmto assess risk- Use antithrombotic therapy as appropriate- Initiate antithrombotictherapy without minimaldelay in patients newlydiagnosed with AF

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:

• Age >65 with no high risk factors

• Age <75 with hypertension, diabetes or vascular disease

Low risk:

• Age <65 with no moderate or high risk factors

Assess for risk of stroke and thromboembolismNICE clinical guideline 36, June 2006

Determine stroke/thromboembolic risk

High risk

Moderate risk

Low risk

Consider anticoagulationConsider anticoagulation

or aspirinAspirin 75 to 300 mg/day

if no contraindications

Contraindications towarfarin?

Warfarin, target INR = 2.5(range 2.0 to 3.0)

Reassess risk stratificationwhenever individual risk

factors are reviewed

NOYES

Patients with AFNICE clinical guideline 36, June 2006

CHADS2 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? How do the harms and benefits of aspirin compare?

How does low dose warfarin compare with adjusted dosing?

What about using clopidogrel instead of aspirin?

How do the harms and benefits of

aspirin compare?

Harms from aspirin Take 1000 patients

6 will have a major extracranial bleeding in 1 year anyway

If they take aspirin 1 more will have a bleed caused by aspirin

Harms from warfarin Take 1000 patients

6 will have a major extracranial bleeding in 1 year anyway

If they take warfarin 3 more will have a bleed caused by warfarin

Anticoagulation Assessment of bleeding risk should be part of clinical

assessment prior to starting anticoagulation

Benefits and potential risks of anticoagulation should be discussed

Aim for INR between 2 and 3

Benefits of aspirin (low risk eg 1% per year) Take 1000 patients

10 will have a stroke in 1 year (1%)

If aspirin is taken 8 will have a stroke

2 will be prevented from having a stroke

Benefits of warfarin (low risk eg 1% per year) Take 1000 patients

10 will have a stroke in 1 year (1%)

If warfarin is taken 4 will have a stroke

6 will be prevented from having a stroke

Benefits of aspirin (moderate risk eg 3.5% per year) Take 1000 patients

35 will have a stroke in 1 year (3.5%)

If aspirin is taken 28 will have a stroke

7 will be prevented from having a stroke

Benefits of warfarin (moderate risk eg 3.5% per year) Take 1000 patients

35 will have a stroke in 1 year (3.5%)

If warfarin is taken 14 will have a stroke

21 will be prevented from having a stroke

Benefits of aspirin (higher risk eg 6% per year) Take 1000 patients

60 will have a stroke in 1 year (6%)

If aspirin is taken 48 will have a stroke

12 will be prevented from having a stroke

Benefits of warfarin (higher risk eg 6% per year) Take 1000 patients

60 will have a stroke in 1 year (6%)

If warfarin is taken 24 will have a stroke

36 will be prevented from having a stroke

How does low dose warfarin compare

with adjusted dosing?

Adjusted dosing is better with no obvious increased harms

What about using clopidogrel instead of

aspirin?

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 2 treatment options

Rate control involves the use of chronotropic drugs or electrophysiological / surgical interventions

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 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

Case detection

Assessment

Rate- contro

l

Rhythm-

control

Referral

Follow-up

Follow-up

OR

Key priority ― choosing the most effective treatmentNICE clinical guideline 36, June 2006

-Some patients with persistent AF will satisfycriteria 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 intoaccount-Antithrombotic therapyshould always be used

Rate control What is it?

Control the ventricular rate (AF remains) How is it done?

Drugs that block AV node conduction (B blockers, Ca channel blockers, digoxin) Why is it done?

Reduce symptoms and myopathy Prevention of embolism & cardiomyopathy

Advantages? As effective as rhythm control Lower risk of adverse events Lower cost Less hospitalisation Avoids antiarrhythmics

Disadvantages? May not remove symptoms Requires anticoagulation Risk of tachycardiomyopathy Atrial remodelling (permanent)

When may it be appropriate? First line particularly in elderly with minimal symptoms Patients at high risk of stroke

Rate control strategy Try rate control 1st for patients with persistent AF :

Over 65 With CHD With contraindications to antiarrhythmic drugs Unsuitable for cardioversion Without CCF

Rhythm control What is it?

Restore and maintain sinus rhythm How is it done?

Electrical / drug conversion (plus maintenance antiarrhythmic drugs) Why is it done?

Reduce symptoms and myopathy Prevention of embolism & cardiomyopathy

Advantages? Better exercise tolerance Improved haemodynamic function Reverse modelling? Less need for, but still requires, antithrombotic treatment

Disadvantages? Difficult to maintain in long term High adverse event rate More hospitalisation High rates of recurrence

When may it be appropriate Young patients New onset AF Where rate control ineffective or symptoms remain

Rhythm control strategy Try rhythm control 1st for patients with persistent AF :

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? 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 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