Atrial fibrillation management in Asia: From the Asian expert forum on atrial fibrillation

Abstract

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is associated with increased morbidity and mortality. AF has a slightly lower incidence and prevalence in Asian populations than in Western populations, but the associated relative risk of stroke and mortality is similar. Patients with AF in Asia have similar disease profiles and CHADS₂ score distributions compared to those in the West, with the exception of a slightly higher prevalence of valvular heart diseases in Asia. Acute ventricular rate control should be the initial consideration in patients with AF and rapid ventricular rate. Anti-arrhythmic drugs have only a modest long-term effect on maintenance of sinus rhythm, and clinical trials in both the West and the East show that chronic rhythm control is not superior to chronic rate control in terms of cardiovascular outcomes, most likely because the benefit of anti-arrhythmic drugs in these trials was often offset by proarrhythmic effects. ECG-driven trials for AF should be replaced by outcome-driven ones. ATHENA is the largest outcome trial to confirm the superiority of a new anti-arrhythmic drug in improving cardiovascular outcomes. The choice of anti-arrhythmic drugs for AF should be based on both safety and efficacy in improving cardiovascular outcomes. For long-term rate control, a lenient strategy with a ventricular rate of less than 110 bpm may be adequate, but more strict rate control may be required if patients continue to complain of symptoms. Catheter ablation should be reserved for patients who remain symptomatic despite optimal medical therapy.

Introduction

Atrial fibrillation (AF) is a cardiac arrhythmia with the following characteristics [1]:

• The surface electrocardiogram (ECG) shows irregular RR intervals (i.e. RR intervals that do not follow a repetitive pattern).

• The surface ECG shows no distinct P waves. (Some apparently regular atrial electrical activity may be seen in some ECG leads, most often in lead V1.)

• The atrial cycle length (i.e. the interval between two atrial activations) is usually variable and less than 300 beats per minute (bpm).

The ventricular response depends on the electrophysiological properties of the atroventricular (AV) node and other conducting tissues, vagal and sympathetic tone, the presence or absence of accessory pathways, and the action of drugs. When AV block or ventricular or AV junctional tachycardia is present, cardiac cycles may be regular. In patients with pacemakers, diagnosis of AF may require pacemaker inhibition in order to expose fibrillatory activity. Irregular, sustained, wide-QRS-complex tachycardia suggests either AF conduction over an accessory pathway or AF with bundle branch block. Atrial flutter is usually readily distinguished from AF. Extremely rapid rates (i.e. greater than 200 bpm) suggest an accessory pathway or ventricular tachycardia [2].

There are five types of AF, which vary in the presentation and duration of the arrhythmia [1].

• First diagnosed AF is what every patient who presents with AF for the first time is considered to have, irrespective of the duration of the arrhythmia or the presence and severity of AF-related symptoms.

• Paroxysmal AF self-terminates, usually within 48 h. Although AF paroxysms may continue for up to 7 days, the 48-hour time point is clinically important because after that point, the likelihood of spontaneous conversion is low and anticoagulation must be considered.

• Persistent AF is present when an AF episode either lasts longer than 7 days or requires termination by cardioversion, either with drugs or by direct current cardioversion.

• Long-standing persistent AF is AF that lasted for at least 1 year before a rhythm control strategy was adopted.

• Permanent AF is said to exist when the presence of the arrhythmia is accepted by the patient (and physician). By definition, rhythm control interventions are not pursued in patients with permanent AF. Should a rhythm control strategy be adopted, the arrhythmia is re-designated as “long-standing persistent AF”.

Detection during the arrhythmia episode can be achieved with a 12-lead ECG, by Holter monitoring, by telemetry recording, or with an event recorder. Patients at risk for AF are encouraged to feel their pulse when they experience palpitations. If the pulse feels rapid and irregular, they should have the irregularity confirmed either with a 12-lead ECG, a Holter or an external event recorder.

Patients with known AF should have at least a 12-lead ECG performed at each clinic visit, the objective being to evaluate the efficacy of treatment strategies. For patients being treated with rhythm management, the ECG serves to confirm treatment efficacy and monitor the QT duration for proarrhythmia effects of the antiarrhythmic agents. For patients being treated with a rate control strategy, a 24-hour Holter can be used to confirm adequate rate control.