In this multi centre pilot study we will perform TEE in patients with AF who are eligible for VKA treatment. TTE will be used as pre-screening: if TTE shows left atrial abnormalities or aortic plaque, patients will be excluded from randomisation. TEE will be performed in all other patients to detect or exclude complex aorta plaques or signs of left atrial stasis. Three hundred patients who do not have these features on TTE will be randomly assigned to treatment with aspirin or VKA. Follow-up will be 1 year.

BACKGROUND Atrial fibrillation (AF) is an independent risk factor for stroke. Therapy with vitamin K antagonists (VKA) and aspirin reduces the risk of thromboembolism (TE) dramatically. Risk stratification is nowadays based on clinical characteristics. However, many high risk AF patients may actually be at low risk, identified by trans-oesophageal echocardiography (TEE).

HYPOTHESIS A comprehensive strategy of TEE based aspirin treatment in AF patients eligible for VKA therapy is safe and feasible.

OBJECTIVES

1. To show that TEE based aspirin treatment is safe when compared with VKA therapy.
2. To test the feasibility of TEE as a tool to detect all four echocardiographic features of high stroke risk.

METHODS In this multi centre pilot study we will perform TEE in patients with AF who are eligible for VKA treatment. TTE will be used as pre-screening: if TTE shows left atrial abnormalities or aortic plaque, patients will be excluded from randomisation. TEE will be performed in all other patients to detect or exclude complex aorta plaques or signs of left atrial stasis. Three hundred patients who do not have these features on TTE will be randomly assigned to treatment with aspirin or VKA. Follow-up will be 1 year.

EXPECTED RESULTS Application of a new echo-guided antithrombotic strategy as proposed herein is feasible and may help to reduce bleeding whilst stroke prevention is maintained. If the lower limit of the 95% confidence interval of the yearly incidence of the primary endpoint on aspirin remains below 4.4% then a large multi centre randomised controlled trial will be performed.

Inclusion Criteria:

• Documented atrial fibrillation or atrial flutter, paroxysmal or permanent
• Conventional indication for VKA treatment
• Signed informed consent

Exclusion Criteria:

• Planned electro cardioversion
• Very high risk of TE (previous ischemic stroke or systemic TE, symptoms of heart failure or left ventricular dysfunction, mitral valve stenosis, hypertrophic cardiomyopathy)
• Indication for VKA treatment other than atrial fibrillation (e.g. mechanic valve prosthesis)
• Atrial fibrillation secondary to reversible diseases (e.g. thyrotoxicosis)
• Contraindication for treatment with VKA, aspirin, or clopidogrel