Table 2 Study inclusion and exclusion criteria

Inclusion criteria

• Aged 75 years or over.

• Atrial fibrillation or flutter confirmed by a study ECG or ECG taken within 2 years of the practice start-up visit.

Absolute exclusion criteria

• Rheumatic heart disease.

• Major non-traumatic haemorrhage (e.g. gastro-intestinal).

• Intra-cranial haemorrhage.

• Oesophageal varices.

• Endoscopically proven peptic ulcer disease in previous year.

• Known allergic hypersensitivity to either of the study medications.

• Patient is known to be terminally ill.

Temporary exclusion criteria

• Uncontrolled hypertension (BP > 180 systolic or 110 diastolic). In such circumstances, the patient will be eligible once the hypertension has been brought under control.

• Recent surgery or head injury (i.e. in last three months). In such circumstances, patient will be eligible once three months had elapsed.

Other relevant factors

1. Poor memory / cognitive function which is defined here as a score of 10 or more on the short orientation-memory concentration test [37]. If the patient does not 'pass' this test, but has a carer who is responsible for the patient's medication, then they are eligible for the trial.

2. Alcohol dependency (30 units per week or more) or binge drinking (10 units at a time).

3. Poorly controlled epilepsy such that the patient is at significant risk of head injury.

4. Risk of falls likely to result in head injury.

5. Long term use of non-steroidal anti-inflammatory agents (NSAIDs). In this circumstance, patients who are on NSAIDs with a lower risk of gastro-intestinal haemorrhage such as ibuprofen, diclofenac or naproxen [40]. are eligible. Given the risks associated with the long term use of NSAID therapy in older age people with atrial fibrillation, consideration should be given to changing patients to alternative medication, and then reviewing trial eligibility.

6. Factors known to increase risk of stroke in these patients: previous stroke or transient ischaemic attack, known heart failure, systolic BP greater than 150 mmHg or diabetes.