MRCGP Exam Update - Anticoagulation and AF

- The prevalence of atrial fibrillation (AF) doubles with each advancing decade from the age of 50. It is an independent risk factor for developing a stroke; its presence increases the risk five-fold.

- The most important decision to be made for a patient with AF is whether or not they should be anticoagulated.

- Anticoagulation is crucial for prevention of thromboembolic complications; the choice of antithrombotic agent depends on the patient's age, co-morbidities and cardiac status.

WHAT IS THE EVIDENCE?

- Warfarin is underprescribed, especially in elderly patients; the benefits of anticoagulation may be greater in such patients (BMJ 2005; 330: 238-43).

CURRENT SITUATION

- Patients with non-valvular AF who have an INR of 2.0 or greater reduce both their future frequency and severity of ischaemic stroke and also the risk of death from stroke (NEJM 2003; 349: 1,019).

- Patients with AF who took warfarin and maintain their INR between 2 to 3 have been shown to have fewer ischaemic strokes, less severe strokes and are less likely to die, compared to those taking lower doses of warfarin, aspirin or no treatment.

- The thrombin inhibitor, ximelagatran, may be a realistic alternative to warfarin. Ximelagatran has the advantage of being a fixed dose and does not require monitoring. The SPORTIF III study was a large study involving over 3,400 patients across 23 countries (Lancet 2003; 362: 1,691).

The results found that ximelagatran was at least as effective as well-controlled warfarin in the prevention of all strokes or systemic embolic events. There were also similar rates of disabling or fatal stroke, TIAs, MI and mortality between the two treatment groups.

- There are some concerns raised about the lack of blinding in the SPORTIF III trial. It is therefore reassuring that the double-blind SPORTIF V trial has produced similar outcomes (Circulation 2003; 108: 2,723).

- A recent study has shown that a doctor's experience with bleeding events associated with warfarin can influence their future prescribing of warfarin - those who had a patient with an adverse bleeding event were 21 per cent less likely to prescribe warfarin (BMJ 2006; 332: 141).

IMPLICATIONS FOR PRACTICE

- Anticoagulation is clearly indicated in patients with valvular heart disease.

- Patients without valvular heart disease are at increased embolic risk if they have one or more of the following: they are 65 years old or older, they have previous embolic event/s, diabetes or hypertension.

- If any of these risk factors are present then the benefits of warfarin outweigh the risks and it should be given unless there are specific contraindications.

USEFUL WEBSITE

www.prodigy.nhs.uk/guidance.asp?gt=atrial%20;fibrillation - PRODIGY Guidance on AF.

KEY POINTS
- AF is very common.
- Warfarin is underprescribed in elderly AF patients.
- Ximelagatran appears to be a promising alternative.
- Patients' preferences should be addressed.

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