100 QUESTIONS IN CARDIOLOGY

67 How long should someone with atrial

fibrillation be anticoagulated before DC

cardioversion, and how long should this be

continued afterwards?

Suzanna Hardman and Martin Cowie

For years, the rationale for a period of anticoagulation prior to

cardioversion was that the anticoagulation would either stabilise

or abolish any thrombus, the assumption being that thrombo-

emboli associated with cardioversion occurred when effective

atrial contraction was restored, dislodging pre-existing thrombus.

Furthermore, it was assumed that recent onset atrial fibrillation

was not associated with left atrial (LA) or left atrial appendage

(LAA) thrombus and could therefore be safely cardioverted

without anticoagulation. Although this has become standard

clinical practice it is not evidence-based and not without hazard.

With anticoagulation most thrombus appears to resolve rather

than to organise. In patients with non-rheumatic atrial fibrillation

most atrial thrombi will have resolved after four to six weeks of

anticoagulation but persistent thrombus has been reported. Left

atrial thrombus is present in a significant proportion of patients

with recent onset atrial fibrillation and the associated thrombo-

embolic rate is similar to that found in patients with chronic atrial

fibrillation. Furthermore, cardioversion itself is associated with

the development of spontaneous contrast and new thrombus and,

in the absence of anticoagulation, even those patients who have

had thrombus excluded using transoesophageal echocardiography

have subsequently developed symptomatic thromboemboli.

For most patients a period of 4 to 6 weeks of anticoagulation

and a transthoracic echocardiogram prior to cardioversion will be

sufficient. Patients at high risk of thrombus (e.g. those with

cardiomyopathy, mitral stenosis or previous thromboembolism)

should undergo a transoesophageal study prior to cardioversion.

In certain patients there may be cogent arguments for minimising

the period of anticoagulation. In these patients transoesophageal

echocardiography can be undertaken and provided no thrombus

is identified will abolish the need for prolonged anticoagulation

prior to cardioversion. However, all patients with atrial

fibrillation need to be fully anticoagulated at the time of

cardioversion and for a period thereafter.