Cardiovascular

Atrial Fibrillation

Disorganised atrial electrical activity abolishes coordinated atrial contraction, so the atrioventricular node is bombarded irregularly and blood stagnates in the left atrial appendage.

In a nutshell

Atrial fibrillation is an irregularly irregular rhythm with no consistent P waves. Cardiovert immediately if it is causing a life-threatening feature, otherwise rate control with metoprolol 50 mg orally 2 to 3 times daily and score stroke risk separately.

Classic presentation

An older adult with palpitations, breathlessness or an incidental irregularly irregular pulse, whose 12-lead ECG shows irregular RR intervals and no consistent P waves.

Key points

CHA2DS2-VASc estimates yearly stroke risk from AF and decides one thing: whether to offer lifelong anticoagulation. ORBIT estimates bleeding risk and decides which bleeding risks you correct first.
CHA2DS2-VASc: age 75 or over, prior stroke, TIA or thromboembolism score 2 each. Heart failure, hypertension, diabetes, vascular disease, age 65 to 74, female sex score 1 each; maximum 9.
ORBIT components are older age, anaemia or reduced haemoglobin, previous bleeding, impaired renal function and antiplatelet treatment. A high score never vetoes anticoagulation on its own.
Rate control is first line except in 5 NICE situations: a reversible cause; heart failure primarily caused by AF; new-onset AF; flutter suitable for ablation; rhythm control judged clinically better.
Ejection fraction above 40% allows a beta-blocker, verapamil, diltiazem or digoxin. Below 40%, only a beta-blocker or digoxin.
Diltiazem for rate control is off-label and the BNF monograph carries no arrhythmia dose. Metoprolol, verapamil and digoxin all have one.
Refer within 4 weeks of failed treatment or recurrence after cardioversion. Ablation follows drug treatment that failed, was unsuitable or was not tolerated; appendage occlusion only when anticoagulation is contraindicated.
Group 1 driving: no driving for at least 4 weeks if the arrhythmia caused or may cause incapacity, and notify the Driver and Vehicle Licensing Agency (DVLA).

First-line investigation

A 12-lead ECG showing irregular RR intervals with no consistent P waves, with the QRS complex, the ventricular part of the trace, usually narrow at under 0.12 seconds.

Management

Unstable AF

ABCDE (airway, breathing, circulation, disability, exposure), monitor ECG, blood pressure and oxygen saturation, oxygen only if saturation is under 94%, intravenous access, 12-lead ECG, correct reversible causes.⁴
Life-threatening features: shock, syncope with severe or ongoing hypotension, myocardial ischaemia, severe heart failure with pulmonary oedema, or immediately after return of spontaneous circulation.⁴
If AF is causing one, give synchronised cardioversion at maximum defibrillator output, up to 3 attempts, without waiting for anticoagulation. Sedate or anaesthetise only if that does not delay treatment.^1,8,4
If 3 shocks fail: amiodarone 300 mg intravenously over 10 to 20 minutes, or procainamide 10 to 15 mg/kg (maximum 1 g) over 20 minutes, then shock again with expert help.⁴

Stable AF: rate control with doses

Confirm rhythm, onset and ejection fraction, and treat triggers: hypoxia, sepsis, ischaemia, pulmonary embolism, thyrotoxicosis, electrolyte disturbance. Rate control is first line unless a NICE exception applies.^1,4
Metoprolol 50 mg orally 2 to 3 times daily, up to 300 mg daily. Acutely, up to 5 mg intravenously at 1 to 2 mg/minute, repeatable once, total 10 to 15 mg.^9,1
Verapamil 5 to 10 mg by slow intravenous injection over 2 minutes, 3 minutes if elderly, repeatable with 5 mg after 5 to 10 minutes. Orally 40 to 120 mg 3 times daily.¹⁰
Digoxin 0.75 to 1.5 mg orally in divided doses over 24 hours to load, then 125 to 250 micrograms daily. Suits a sedentary person; less effective on exertion.^11,1
Never give intravenous verapamil after an intravenous beta-blocker: simultaneous intravenous beta-blockade is a listed contraindication. In acute decompensated heart failure get senior input and use no calcium-channel blocker.^10,1
If monotherapy fails, combine any 2 of a beta-blocker, diltiazem and digoxin. Do not use amiodarone for long-term rate control. Doses are adult; adjust for renal and hepatic function.¹

Cardioversion timing

Definite onset under 48 hours allows rate or rhythm control. Over 48 hours or uncertain: rate control, plus at least 3 weeks of therapeutic anticoagulation before planned cardioversion, or a transoesophageal echocardiography (TOE)-guided strategy.¹
Beyond 48 hours NICE prefers electrical cardioversion. If a drug is used: flecainide or amiodarone without structural or ischaemic heart disease, amiodarone if structural disease is present.^1,12
The acute algorithm prompts anticoagulation when the arrhythmia has lasted more than 24 hours. NICE's 48 hours governs cardioversion timing; the 24 hours governs anticoagulation. Instability overrides both.^4,1

Prevent stroke, with the dose-reduction rules

Offer a direct-acting oral anticoagulant (DOAC) at a CHA2DS2-VASc score of 2 or more, and consider one for a man scoring 1.^1,2
Do not anticoagulate someone under 65 whose only risk factor is their sex, which is a score of 0 in men and 1 in women.¹
Apixaban 5 mg twice daily. Reduce to 2.5 mg twice daily if at least 2 of: age 80 years or over, weight 60 kg or less, serum creatinine 133 micromol/litre or more.⁷
Apixaban is also 2.5 mg twice daily at creatinine clearance 15 to 29 mL/minute whatever the age or weight. Avoid apixaban and rivaroxaban below 15 mL/minute.^7,13
Rivaroxaban 20 mg once daily with food. Reduce to 15 mg once daily if creatinine clearance is 15 to 49 mL/minute.¹³
Edoxaban 60 mg once daily. Reduce to 30 mg once daily by any single one of: creatinine clearance 15 to 50 mL/minute, weight 60 kg or less, or ciclosporin, dronedarone, erythromycin or ketoconazole.¹⁴
Dabigatran is the fourth NICE option; take its dose and thresholds from the BNF monograph. Check creatinine clearance, weight, interactions and adherence before any DOAC prescription.^1,7
Vitamin K antagonist only when a DOAC is contraindicated, not tolerated or unsuitable. Warfarin 5 to 10 mg on day 1, maintenance 3 to 9 mg daily, same time each day.^1,15
A mechanical valve or moderate-to-severe mitral stenosis means a vitamin K antagonist: edoxaban is not recommended in either and apixaban is contraindicated with a prosthetic valve.^14,7
Reassess warfarin if time in therapeutic range is under 65%, or after 2 INR values above 5, 1 above 8, or 2 below 1.5 within 6 months.¹
New-onset AF on no or subtherapeutic anticoagulation: heparin at first presentation, for example enoxaparin 1.5 mg/kg subcutaneously every 24 hours. It runs alongside emergency cardioversion, not instead of it.^1,16
If the presentation is acute ischaemic stroke, follow the stroke pathway: no routine anticoagulation, and aspirin 300 mg for 2 weeks first in disabling stroke with AF.^6,1

Pre-excited AF

An irregular, very rapid broad-complex rhythm with varying QRS morphology is possible pre-excited AF. Verapamil and digoxin are contraindicated: accessory-pathway conduction increases and ventricular tachycardia may be precipitated.^10,11,5
Avoid adenosine, diltiazem and beta-blockers too. The acute route is procainamide or synchronised cardioversion, and amiodarone is not among the listed options. Get urgent expert help.^4,5

When to involve cardiology

Refer within 4 weeks of failed treatment or recurrence after cardioversion, and for symptoms despite adequate rate control, drug intolerance or suspected tachycardia-induced cardiomyopathy.¹
Left-atrial catheter ablation: symptomatic paroxysmal or persistent AF when drugs are unsuccessful, unsuitable or not tolerated. Left atrial appendage occlusion: only when anticoagulation is contraindicated or not tolerated.¹

Disposition, driving and review

Monitor after acute treatment or cardioversion and record a post-treatment ECG. Admit after instability, uncontrolled rate, acute heart failure or ischaemia, pre-excitation or a treatment complication.¹
Group 1 licence: no driving for at least 4 weeks if the arrhythmia caused or may cause incapacity, and notify the DVLA. At least 2 days after other catheter ablation, with no need to notify.¹⁷
Group 2 bus and lorry additionally needs the cause treated, 3 months free of incapacitating arrhythmia and an ejection fraction of at least 40%. Review anticoagulation at least annually.^17,1

Exam traps

A regular pulse does not exclude AF: ventricular pacing, complete atrioventricular block or successful rhythm control can regularise it.
Under 65 with sex as the only risk factor, the answer is no anticoagulation, not a DOAC.
Apixaban needs 2 of 3 criteria to halve the dose; edoxaban needs only 1 of 3. Getting these the wrong way round overdoses a small elderly woman.
A mechanical valve or moderate-to-severe mitral stenosis means a vitamin K antagonist, not a DOAC.
Restored sinus rhythm does not justify stopping anticoagulation, because AF recurs silently.
Aspirin monotherapy is explicitly not an option for AF stroke prevention, even when a DOAC feels too risky.
A high ORBIT score prompts correction of modifiable bleeding risks, not withholding. Age or falls alone are never grounds to withhold.
Intravenous verapamil after an intravenous beta-blocker is contraindicated and risks profound bradycardia or asystole.
In an irregular broad-complex tachycardia, verapamil and digoxin are contraindicated, and amiodarone is not the safe substitute.
NICE bans amiodarone for long-term rate control, which is different from its acute and specialist rhythm-control roles.

Illustrations

ECG in atrial fibrillation12-lead ECG showing irregular RR intervals and no consistent P waves. A broad or varying QRS morphology should prompt assessment for aberrancy, bundle branch block or pre-excitation rather than being assumed to be uncomplicated AF.CardioNetworks: [ ], Wikimedia Commons · CC-BY-SA-3.0

Chaotic atrial activation and appendage stasisDiagram linking disorganised atrial activation to an irregular ventricular response, loss of atrial systole and left-atrial-appendage stasis.PassFinals · original

Rate, rhythm and stroke-prevention decisionsFlow diagram separating haemodynamic stabilisation, rate or rhythm control, and the independent anticoagulation decision.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.