Drug Therapy for the Management of Atrial Fibrillation: An Update

Andrew RJ Mitchell

Disclosures

Br J Cardiol. 2003;10(5) 

In This Article

Anticoagulation

A meta-analysis of 16 trials of antithrombotic strategies including 9,874 participants was published in 1999.[54] The investigators concluded that adjusted-dose oral anticoagulation was highly effective at preventing stroke (both ischaemic and haemorrhagic) in patients with AF with a risk reduction of 61% (95% CI, 47% to 71%) vs. placebo. Aspirin reduced stroke by 22% (CI, 2% to 38%). The mean follow-up, however, was 1.7 years, which is considerably shorter than the period usually seen in clinical practice. It is also unclear if the low rates of major haemorrhage observed in these carefully managed trials correspond to the older population (whose anticoagulation therapy is often less closely regulated) seen in practice in the UK. Indeed, an analysis of quality adjusted life expectancy and cost in the oldest old has indicated that there remains no evidence that routine anticoagulation in the very elderly is beneficial.[55]

Current guidelines recommend the continuation of anticoagulation for three to four weeks after cardioversion if the arrhythmia episode lasted longer than 48 hours.[4] This is because following conversion of AF to sinus rhythm there is a period of transient mechanical dysfunction of the left atrium and atrial appendage, known as 'stunning'.[56] Due to the high relapse rate after cardioversion it may be more appropriate to continue anticoagulation for a longer period.[57] The differences in stroke rates noted in the AFFIRM study may be as a consequence of the early discontinuation of anticoagulation in the rhythm control group. An approach using transoesophageal echocardiography to exclude left atrial thrombus was shown to reduce the time to cardioversion (three days vs. 31 days) without any increase in thrombo-embolic rate.[58] A reduction in haemorrhagic events (particularly gastrointestinal) was also noted, probably as a consequence of shorter duration of warfarin usage. This strategy now offers the opportunity to cardiovert AF of more than 48 hours duration without having to wait a month for anticoagulation with warfarin.

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