Atrial Fibrillation

Introduction

Atrial fibrillation is a common supraventricular tachyarrhythmia caused by uncoordinated atrial activation and associated with an irregular ventricular response.

Atrial fibrillation is classified according to clinical pattern, with patients sometimes progressing from one pattern to another.

Patients with AF may have various symptoms but 50-87% are initially asymptomatic, with possibly a less favourable prognosis.

Risk Factors

The ABC Pathway

The simple Atrial fibrillation Better Care (ABC) holistic pathway streamlines integrated care of AF patients across all healthcare levels and among different specialties. Compared with usual care, implementation of the ABC pathway has been significantly associated with lower risk of all-cause death, composite outcome of stroke/major bleeding/cardiovascular death and first hospitalization, lower rate of cardiovascular events and lower health-related cost.

• A - Anticoagulation/Avoid Stroke
• B - Better symptom control
• Rate control
• Rhythm control
• C - Cardiovascular and comorbidity optimization

Anticoagulation

Thromboembolism is a major complication of AF which may result in stroke or death.

Common stroke risk factors are summarized in the clinical risk-factor-based CHA₂DS₂-VASc. The CHA₂DS₂-VASc performs only modestly in predicting high-risk patients who will sustain thromboembolic events, but those identified as low-risk [CHA₂DS₂-VASc 0 (males) or score of 1 (females)] consistently have low ischemic stroke or mortality rates (<1%/year) and do not need any stroke prevention treatment.

Several risk scores for bleeding, such as the HAS-BLED score, have been developed to assist in determining the harm-benefit balance of anticoagulant therapy for patients with AF. However, a high bleeding risk score should not lead to withholding oral anticoagulants. Modifiable bleeding risk factors should be managed and high-risk patients with non-modifiable bleeding risk factors (HAS-BLED score ≥3) should be reviewed earlier (for instance in 4 weeks rather than 4-6 months) and more frequently.

The few absolute contraindications to oral anticoagulants include active serious bleeding, associated comorbidities (severe thrombocytopenia, severe anaemia under investigation, etc), or a recent high-risk bleeding event such as intracranial haemorrhage.

NOTE: Antiplatelet therapy alone (monotherapy or aspirin in combination with clopidogrel) is not recommended for stroke prevention in AF.

Rate Control

Rate control is an integral part of AF management and is often sufficient to improve AF-related symptoms. In general, lenient rate control (heart-rate target <110 bpm) is an acceptable initial approach, regardless of HF status (with the exception of tachycardia-induced cardiomyopathy), unless symptoms call for stricter for rate control.

Pharmacological rate control can be achieved with

• Beta-blockers - often first line
• Non-dihydropyridine calcium channel blockers (e.g. diltiazem and verapamil) - first line treatment in severe asthma or COPD; not suitable in AF patients with LVEF <40%
• Digoxin
• Some antiarrhythmic drugs also have rate-limiting properties (e.g. amiodarone, dronedarone, sotalol) but generally they should be used only for rhythm control.

Ablation of the atrioventricular node and pacemaker implantation can control ventricular rate when medication fails.

Rhythm Control

The "rhythm control strategy" refers to attempts to restore and maintain sinus rhythm and may engage a combination of treatment approaches along with an adequate rate control, anticoagulation therapy and comprehensive cardiovascular prophylactic therapy (upstream therapy, including lifestyle and sleep apnoea management).

• Cardioversion
• Antiarrhythmic medication
• Restoration of sinus rhythm: Flecainide, propafenone, vernakalant, amiodarone, ibutilide
• Long-term maintenance of sinus rhythm: Amiodarone, flecainide, propafenone, dronedarone, sotalol, disopyramide
• Catheter ablation

The primary indication is to reduce AF-related symptoms and improve quality of life.

Cardiovascular Risk Factors and Concomitant Diseases: Detection and Management

Management of risk factors and cardiovascular disease complements stroke prevention and reduces AF burden and symptom severity.

External Links

• ESC Guidelines for the diagnosis and management of Atrial Fibrillation, 2020
  
• Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the euro heart survey on atrial fibrillation, 2010
  
• A Novel User-Friendly Score (HAS-BLED) To Assess 1-Year Risk of Major Bleeding in Patients With Atrial Fibrillation: The Euro Heart Survey, 2010