100 QUESTIONS IN CARDIOLOGY

63 What drugs should be used to maintain

someone in sinus rhythm who has paroxysmal

atrial fibrillation? Is there a role for digoxin?

Suzanna Hardman and Martin Cowie

The natural history of patients with paroxysmal atrial fibrillation

is that over a period of time (and often many years) there is a

gradual tendency to an increased frequency and duration of

attacks. A proportion of patients will develop chronic atrial

fibrillation. Not all patients require antiarrhythmic drugs and the

potential side effects and inconvenience of regular medication

must be balanced against the frequency of episodes and

symptomatology which vary markedly between patients.

Triggers include alcohol and caffeine, ischaemia, untreated

hypertension (which if aggressively managed can at least in the

short term obviate the need for antiarrhythmics), thyrotoxicosis,

and in a small proportion of patients vagal or sympathetic stimu-

lation where attacks are typically preceded by a drop in heart rate

or exercise respectively.

The most effective drugs are also those with potentially

dangerous side effects. The risks of class 1 agents (such as

flecainide, disopyramide and propafenone) in patients with

underlying coronary artery disease are well recognised and are

best avoided. In younger patients (where it is presumed the

associated risks are proportionately less) they can be highly

effective. Sotalol may be useful in some patients but adequate

dosing is required to achieve class 3 antiarrhythmic activity and

not all patients will tolerate the associated degree of beta

blockade. Amiodarone can be highly effective but its use is

limited by the incidence of serious side effects. Beta blockers and

calcium channel blockers have no role in preventing paroxysms

of atrial fibrillation but can help certain patients in reducing the

rate and so symptomatology.

Despite the long-standing conviction of many clinicians that

digoxin is efficacious in the management of paroxysmal atrial

fibrillation it has been clearly shown that digoxin neither reduces

the frequency of attacks nor produces any useful reduction of

heart rate during paroxysms of atrial fibrillation. Furthermore a

number of placebo-controlled studies designed to explore the

possibility that digoxin might chemically cardiovert patients