Start or STop Anticoagulants Randomised Trial (SoSTART)

Inclusion Criteria:

1. Patient age ≥18 years
2. Symptomatic intracranial haemorrhage (i.e. intracerebral haemorrhage, non-aneurysmalsubarachnoid haemorrhage,intraventricular haemorrhage, or subduralhaemorrhage)

• Not attributable to a known underlying intracranial aneurysm, arteriovenousmalformation, cerebral cavernous malformation, dural arteriovenous fistula,intracranial venous thrombosis
• Not attributable to known head injury, based on:
• a history from the patient/witness of spontaneous symptom onset without precedinghead trauma (head trauma occurring after symptom onset is permissible)
• brain imaging appearances consistent with spontaneous intracranial haemorrhage (which may be accompanied by the brain/bone/soft tissue appearances of traumaoccurring subsequently)

3. Atrial fibrillation/flutter (persistent or paroxysmal) with a CHA2DS2-VASc score ≥2
4. If included in the brain magnetic resonance imaging (MRI) sub-study, the scan must bedone after symptomatic intracranial haemorrhage and before randomisation

Exclusion Criteria:

1. Symptomatic intracranial haemorrhage within the last 24 hours (when the risk ofhaemorrhage expansion/growth is greatest)
2. Symptomatic intracranial haemorrhage is exclusively due to trauma or haemorrhagictransformation of ischaemic stroke
3. Prosthetic mechanical heart valve or severe (haemodynamically significant) nativevalve disease
4. Left atrial appendage occlusion for prevention of systemic embolism in AF done in thepast, or intended to be performed
5. Intention to start antiplatelet drug(s) if randomised to start full dose OAC
6. Intention to start OAC or parenteral anticoagulation
7. Intention to implement the allocated treatment strategy for <1 year
8. Patient or their doctor is certain about whether to start or avoid full dose OAC
9. Brain imaging that first diagnosed the intracranial haemorrhage is not available
10. Patient is not registered with a general practitioner
11. Patient is pregnant, breastfeeding, or of childbearing age and not takingcontraception
12. Patient and carer unable to understand spoken or written English
13. Contraindications to any of the IMPs, other than recent intracranial haemorrhage
14. Contraindication to MRI (brain MRI sub-study)
15. Life expectancy less than one year
16. Previously randomised in SoSTART