Atrial fibrillation

Definition

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia resulting from irregular, disorganized electrical activity and ineffective contraction of the atria.

It results from irregular, disorganized electrical activity in the atria, leading to an irregular ventricular rhythm.

The ventricular rate of untreated AF is around 160–180bpm.

Paroxysmal AF
Episodes >30s but <7d (often less than 48 hours) that are self-terminating and recurrent.

Persistent AF
Episodes >7 days or <7d but requiring pharmacological or electrical cardioversion.

Permanent AF
AF that fails to terminate using cardioversion
AF that is terminated but relapses within 24 hours
Longstanding AF (>1 year) in which cardioversion has not been indicated or attempted

Prevalence

AF is the most common cardiac arrhythmia, affecting 2.5% of the population
Men>Women
At age 40 years, lifetime risks for AF were around 26.0%

Causes

Cardiac conditions:
Ischaemic heart disease
Hypertension
Valvular heart disease
Congestive heart failure
Pre-excitation syndromes (such as Wolff–Parkinson–White syndrome).
Sick sinus syndrome
Inflammatory or infiltrative disease (such as pericarditis, amyloidosis, or myocarditis)
Rheumatic valvular disease
Atrial or ventricular dilation or hypertrophy.

Non-cardiac conditions:
Acute infection
Hyperthyroidism
Electrolyte depletion (such as hypokalemia and hyponatremia)
Cancer (primary or secondary metastases to the pericardium)
Pulmonary embolism
Diabetes mellitus
Alcohol abuse

Complications

  • Stroke (2.3-fold increased risk of stroke)

  • Thromboembolism

  • Heart failure

  • Tachycardia-induced cardiomyopathy and critical cardiac ischaemia (from the persistently elevated ventricular rate seen in uncontrolled AF)

  • Reduced quality of life

The risks from paroxysmal AF are similar to those from persistent or permanent AF.

AF accounts for 15% of all ischaemic strokes and 33% of strokes in the elderly

Diagnosis

Clinically

Irregular pulse on manual pulse palpation
+/- SOB, palpitations, chest discomfort, syncope or dizziness
+/- Reduced exercise tolerance, malaise/listlessness, decrease in mentation, or polyuria
+/- Complication of AF (stroke, TIA, or heart failure)

Diagnostic accuracy of irregular pulse on palpation for detecting atrial fibrillation

Sensitivity 95%-100%
Specificity 71%-79%
Positive predictive value 12%-23%
Negative predictive value 100%, 99% : AF can be confidently excluded if irregular pulse is absent

Irregular pulse present—> high FP rate—>low specificity and low PPV [SpPin]
Irregular pulse absent —> low FN rate—> high sensitivity and high NPV [SnNout]

  1. Confirm AF by ECG or Ambulatory ECG
    No P-waves, a chaotic baseline, and an irregular ventricular rate.
    If paroxysmal AF is suspected arrange 24-hour ambulatory ECG monitor and/or 7-day Holter monitor

  2. Check BP (hypertension)

  3. Chest X-ray if lung pathology is suspected

  4. Bloods: LFTs (excess alcohol intake), TFTs (hyperthyroidism), electrolyte depletion (Na, K, Ca, Mg. eGFR), CRP (infection), glucose and HBA1c (diabetes mellitus)

  5. Echocardiogram: Identify any structural heart disease (valve disease) or functional heart disease (such as heart failure) that will influence subsequent management (for example choice of antiarrhythmic drug).

Differential diagnosis of an irregular pulse

Atrial flutter
Atrial extrasystoles
Ventricular ectopic beats
Sinus tachycardia
Supraventricular tachycardias: atrial tachycardia, atrioventricular nodal re-entry tachycardia, and Wolff-Parkinson-White syndrome
Multifocal atrial tachycardia
Sinus rhythm with premature atrial or ventricular contractions

Management (non-valvular Atrial Fibrillation)

Symptomatic acute onset AF (onset <48hr) —> ADMIT, consider emergency electrical cardioversion.[Symptomatic: haemodynamic instability (HR>150, SBP<90), loss of consciousness, SOB, chest pain]

In patients with severe symptoms or a serious complication (such as stroke, heart failure, pulmonary embolism, pneumonia, or thyrotoxicosis) —> ADMIT

Principles

  1. Identifying and managing any underlying causes

  2. Treating the arrhythmia (rate vs rhythm control)

  3. Stroke risk stratification and oral anticoagulation decision-making.
    Assessing stroke risk using the CHA2DS2VASc assessment tool
    The HAS-BLED assessment tool should be used to assess the risk of major bleeding.
    Omit anticoagulation in AF with low risk of stroke (CHA2DS2-VASc=0 in males or 1 in females)

  4. Anticoagulants
    Factor X inhibitor: Apixaban, rivaroxaban
    Factor II inhibitor: Dabigatran
    Vitamin K antagonist: Warfarin
    Anticoagulation treatment reduces the risk of stroke by about two-thirds
    If anticoagulation contraindicated, or poor anticoagulation control with warfarin, or DOAC contraindicated or not tolerated, then recommend left atrial appendage occlusion.

    Do not withhold anticoagulation solely because the person is at risk of having a fall

  5. Manage cardiovascular (hypertension, diabetes, hyperlipidaemia) and other co-morbidities (obesity, lifestyle, obstructive sleep apnoea).

 

Rate-control vs. Rhythm-control treatment

There is no evidence that rhythm-control is superior to rate-control in preventing stroke or reducing mortality. Therefore, the main treatment objective is control of symptoms.

 

Rhythm-control AF
Recommended for:
1) AF with a reversible cause (e.g. chest infection)
2) Heart failure caused/worsened by AF
3) New-onset AF
Drugs: amiodarone, flecainide and sotalol (secondary care)

Rate-control AF
Recommended for most patients

1st line: Beta-blocker or rate-limiting calcium-channel blocker
2nd line: Digoxin for people with non-paroxysmal AF only if they are sedentary

 

Beta-blockers: atenolol (isolated AF, AF and previous MI), bisoprolol (AF and heart failure, AF and diabetes) as it is cardioselective.

Rate-limiting calcium-channel blocker: diltiazem (off-label), verapamil.
However, rate-limiting calcium-channel blockers are contraindicated in people with co-existing heart failure.

Amiodarone and sotalol are initiated by secondary care

Follow-up

  1. Treatment initiation. Within 1 week of starting rate-control treatment (or any dose alteration), check that the person is tolerating the drug, and review symptoms (such as palpitations, breathlessness, and fatigue), heart rate, and blood pressure.

  2. Check symptomatic control and compliance: manage drug interactions and adverse effects. Ventricular rate should be controlled between 60 and 80 at rest and between 90 and 115 during moderate exercise.

  3. Stoke Risk. Reassess the person's stroke risk using the CHA2DS2VASc assessment tool and bleeding risk using the HAS-BLED score tool, at least annually. Consider left atrial appendage occlusion (catheter-based technique) if anticoagulation is contraindicated or not tolerated.

Referral to a cardiologist should be made if:

  1. Rhythm-control is appropriate (reversible cause, heart failure, new-onset AF)

  2. Rate-control treatment fails to control the symptoms of AF (prompt referral within 4 weeks), even if heart rate has been controlled. Secondary care options include pharmacological or electrical rhythm control (DC cardioversion, left atrial catheter ablation, pacing followed by atrioventricular node ablation) or both.

  3. The person is found to have valvular disease (valvular AF) or left ventricular systolic dysfunction (AF with heart failure) on echocardiography.

  4. Wolff–Parkinson–White syndrome or a prolonged QT interval indicated by ECG.

Assessing risk of stroke in AF using CHA2DS2VASc assessment tool

  1. Anticoagulant treatment is indicated if CHA2DS2VASc ≥ 2 (taking the HAS-BLED bleeding risk into account).

  2. Anticoagulant treatment should also be considered for CHA2DS2VASc ≥ 1 in men (taking the HAS-BLED bleeding risk into account)

  3. Low-risk patients [CHA2DS2VASc=0 (men) or 1(women)] do not require anticoagulant therapy

CHA2DS2VASc

  • Congestive heart failure/left ventricular dysfunction = 1

  • Hypertension = 1

  • Age ≥75y = 2

  • Diabetes mellitus = 1

  • Stroke/TIA/thromboembolism = 2

  • Vascular disease (prior MI, peripheral arterial disease, or aortic plaque) = 1

  • Age 65–74y = 1

  • Sex category (female) = 1

Where anticoagulation is being considered, assess (and modify risk factors) for major bleed using HAS-BLED assessment tool

To reduce risk of bleeding, modify: uncontrolled hypertension, harmful alcohol consumption, and concurrent use of aspirin or NSAIDs.

  • Hypertension = 1

  • Abnormal liver function (=1) and abnormal renal function (=1)

  • Stroke= 1

  • Bleeding = 1

  • Labile INRs= 1

  • Elderly (aged over 65 years)= 1

  • Drugs (antiplatelet agents, NSAIDs) = 1, Alcohol=1

Notes on warfarin

Starting warfarin: check INR daily or alternate day until INR 2-3 on two occasions, then monitor twice weekly for 2w, followed by weekly until at least two INRs 2-3.

Calculate the time in therapeutic range (TTR) at each visit and over a maintenance period of at least 6 months following initiation and stabilisation.Use a validated method of measurement, such as the Rosendaal method, or proportion of tests in range for manual dosing. Exclude measurements during the first 6w of treatment initiation.

Poor anticoagulation control is indicated by any of the following:

  • TTR < 65%.

  • Two INR values >5 or one INR value > 8 within the past 6 months.

  • Two INR values <1.5 within the past 6 months.

If poor anticoagulation control cannot be improved, consider switching to a direct oral anticoagulant (DOAC; apixaban, edoxaban, dabigatran, or rivaroxaban)

Driving and Flying

Flying
No flying restrictions provided AF is stable and has not recently worsened or become more symptomatic.

Driving

For group 1 entitlement:
Driving must cease if the arrhythmia has caused or is likely to cause incapacity,
Driving may be permitted when the underlying cause has been identified and controlled for at least 4 weeks.

Dr Rajesh VarmaAtrial fibrillation