Atrial fibrillation

Definition and epidemiology. Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, characterised by uncoordinated atrial activation with consequent loss of atrial mechanical function. It is now regarded as a multifactorial disease caused by an interplay of cardiovascular and metabolic risk factors, systemic inflammation, and anatomical and electrical substrates. In 2016 more than 43 million people were estimated to have AF; the lifetime risk at age 55 is about 35%. It is 1.5 times more common in men, though onset is later in women (65 versus 60 years).

Risk factors. All the classical cardiovascular risk factors are significantly associated with incident AF. Each 10 mmHg rise in systolic blood pressure increases the risk of developing AF by 11–16%; in diabetes there is a dose–response relationship between HbA1c and incident AF; and there is a strong association between increasing age and increasing systemic inflammation as measured by C-reactive protein. Others: heart failure, valvular disease (especially rheumatic mitral disease in India), obesity, obstructive sleep apnoea, alcohol, thyrotoxicosis, chronic kidney disease and cardiac surgery. The risk of incident AF is directly related to the total burden of risk factors, rising progressively with the number present.

Clinical features and consequences. Presentation may be with palpitations, breathlessness, fatigue, chest pain, dizziness or syncope, but AF is frequently asymptomatic and detected incidentally — or presents first as stroke, heart failure or falls. In older people the loss of the atrial contribution to ventricular filling is critical, because they depend more on atrial contraction than on ventricular relaxation for left ventricular filling and therefore decompensate rapidly into heart failure. Consequences: up to 30% of all ischaemic strokes are due to AF; 20– 30% of AF patients develop heart failure; there is an up to 60% relative increase in risk of significant cognitive decline; more than 60% report impaired quality of life; and AF causes an up to 3.5-fold increase in cardiovascular and all-cause death. The pulse is irregularly irregular with an apex–radial deficit — but note that frequent atrial ectopic beats, common in the old, can produce a pulse that is confused with AF, so confirm with an ECG and obtain a transthoracic echocardiogram if not previously done.

Diagnosis and assessment. Confirm with a 12-lead ECG showing absent P waves, an irregularly irregular QRS rhythm and a fibrillatory baseline. For paroxysmal AF use Holter monitoring, extended patch monitoring, an implantable loop recorder or a smartphone/wearable single-lead ECG. Classify as first-diagnosed, paroxysmal, persistent, long-standing persistent or permanent. Investigate with echocardiography (left atrial size, valve disease, ejection fraction, left ventricular hypertrophy), thyroid function, full blood count, renal and liver function, electrolytes, and screen for sleep apnoea and alcohol excess.

Anticoagulation — the priority. Assess stroke risk with CHA DS -VASc and bleeding risk with HAS-BLED.

Rate versus rhythm control and integrated care. Rate control is the usual first strategy in the elderly, with a resting target of < 110/min (lenient) tightened to < 80/min if symptoms persist: use a beta-blocker or a rate-limiting calcium channel blocker (diltiazem, verapamil — avoid in heart failure), with digoxin as an add-on, particularly in the sedentary or hypotensive, at reduced dose with level monitoring. Rhythm control is indicated for persistent symptoms despite rate control, recent-onset AF, AF-related heart failure, or a young patient: options are DC cardioversion (with 3 weeks of anticoagulation before and 4 weeks after, or a TOE-guided approach), antiarrhythmic drugs (amiodarone is the most usable in structural heart disease but has thyroid, hepatic, pulmonary, ocular and neurological toxicity in long-term use; flecainide and propafenone only with structurally normal hearts), and catheter ablation, which is more effective than drugs and is reasonable in selected fitter older patients. Pace-and-ablate (AV node ablation with pacing) is an option for refractory rapid AF. Manage the whole patient with the ABC pathway — Avoid stroke with anticoagulation, Better symptom control, Comorbidity and risk factor management, which has been shown to improve outcomes.

The 2024 ESC Guidelines for the Management of Atrial Fibrillation made three examinable changes. First, CHA DS -VASc has been replaced by CHA DS -VA — sex category is removed (maximum 7), with 2 2 2 2 anticoagulation recommended at a score of ≥ 2 and considered at 1, on the grounds that female sex is an age-dependent risk modifier rather than an independent risk factor. Second, the ABC pathway has been reframed as the AF-CARE pathway — Comorbidity and risk factor management, Avoid stroke and thromboembolism, Reduce symptoms by rate and rhythm control, and Evaluation with dynamic reassessment — deliberately placing comorbidity management first. Third, following EAST-AFNET 4 and CASTLE-AF, there is stronger support for early rhythm control within 12 months of diagnosis and for catheter ablation as first-line therapy in paroxysmal AF and in AF with heart failure and reduced ejection fraction.