Atrial Fibrillation

Chaotic and disorganized atrial activity produces an irregular heartbeat

Aetiology

• Hypertension and heart failure are the most common causes in the developed world

• Other causes include MI, hyperthyroidism, rheumatic heart disease, sepsis and electrolyte disturbances

• No cause found in 2-10% (idiopathic) - lone AF

Pathophysiology

• Ectopic foci in the pulmonary veins cause an irregular atrial rhythm between 300-600 bmp

• AV is unable to transmit beats as quickly as this and so does so intermittently, resulting in an irregular ventricular rhythm

• Filling time is reduced which reduces CO - allows stasis of blood which increases stroke risk

Classification of AF

• Paroxysmal = <48 hrs

• Persistent = >48 hrs

• Permanent = unable to cardiovert to NSR

Clinical presentation

Symptoms

• Incidental finding in ~30% of patients

• Can also present with rapid palpitations, dyspnoea and/or chest pain following onset of AF

Signs

• Irregularly irregular pulse

Investigations

ECG

• Atrial rate >300 bmp

• Irregularly irregular rhythm

• No P waves - irregular baseline

• Narrow QRS

CHA2DS2-VASc

• Risk stratifying tool to determine stroke risk and therefore the most appropriate anticoagulation strategy

Management

Acute management

• Carry out emergency electrical cardioversion in patients with life-threatening haemodynamic instability caused by new-onset AF

• In people with AF presenting acutely without life-threatening haaemodynamic instability:
• Offer either rate or rhythm control if the onset of the arrythmia is less than 48 hours
• Offer rate control if onset is more than 48 hours or is uncertain

• As long as there are no contraindications, offer heparin at initial presentation and continue until appropriate anticoagulation according to CHA2DS2-VASc started

Rate control

• All patients with AF should have rate control as first line unless:
• There is a reversible cause for their AF
• Their AF is of new onset
• Their AF is causing heart failure
• They remain symptomatic despite being effectively controlled

• Options for rate control:
1. β-blocker e.g. atenolol is first line
2. CCB e.g. verapamil, diltiazem (not preferable in heart failure
3. Digoxin (only in sedentary people, needs monitoring and risk of toxicity)

• Other: AV node ablation

Rhythm control

• Rhythm control can be offered to patients where:
• There is a reversible cause for their AF
• Their AF is of new onset (>48 hours)
• Their AF is causing heart failure
• They remain symptomatic despite being effectively rate controlled

• Cardioversion
• Immediate vs delayed
• Immediate cardioversion - if AF present for less than 48 hours or patient is severely haemodynamically stable
• Delayed cardioversion - if AF present for more than 48 hours and patient is haemodynamically stable
• Patient should be anticoagulated for a minimum of 3 weeks before cardioversion due to risk of clot formation which may be mobilised by cardioversion
• Should have rate control while waiting
• Pharmacological vs electrical
• Pharmacologial cardioversion - flecanide, amioderone (drug of choice in patients with structural heart disease)
• Electrical cardioversion (DCCV) - sedation and use of a cardiac defibrillator

• Long term medical rhythm control
• β-blocker
• Dronedarone is second line for maintaining normal rhythmwhere patients have had successful cardioversion
• Amiodarone is useful in patients with heart failure or left ventricular dysfunction

• Others: left atrial catheter ablation, Maze procedure

Paroxysmal AF

• Patients with paroxysmal AF may be appropriate for a ‘pill in the pocket’ approach if they have infrequent episodes without any underlying structural heart disease

• Patient takes a pill to terminate their AF only when they feel their symptoms starting - flecanide is the usual treatment

• Should still be anticoagulated according to CHA2DS2-VASc

Anticoagulation

• Long term anticoagulation for patients with AF in order to prevent thromboembolic complications is indicated if the patient has underlying valvular disease and/or CHADSVAS score >2

• Warfarin, DOAC