Here is the design of a clinical trial:

Official Title: Left Atrial Appendage Closure by Surgery-2

Included conditions:
- Stroke, Ischemic
- Atrial Fibrillation

Study Armgroups:
- {'label': 'Closure', 'type': 'ACTIVE_COMPARATOR', 'description': 'Patients randomized to the active Group will undergo closure of the left atrium appendage during Heart surgery by means of commercial clips', 'interventionNames': ['Procedure: closure of the left atrium appendage']}
- {'label': 'Control', 'type': 'NO_INTERVENTION', 'description': 'The left atrium appendage will remain open in patients randomized to the control group'}

Interventions:
- {'type': 'PROCEDURE', 'name': 'closure of the left atrium appendage', 'description': 'closure of the left atrium appendage in addition to the planned Heart operation', 'armGroupLabels': ['Closure']}

Primary Outcomes:
- {'measure': 'Number of participants with Stroke occurrence including Transitory cerebral ischemia (TCI)', 'description': 'Stroke is an acute episode of focal dysfunction of the brain, retina, or spinal cord lasting longer than 24 h, or of any duration if imaging (CT or MRI) or autopsy show focal infarction relevant to the symptoms. Transitory cerebral ischemia (TCI) is defined as above, but with symptoms lasting less than 24 h.\n\nEndpoints will be assigned by two independent neurologists, who are blinded to what procedure the patient undergo. In case of discrepancy, the events will be assigned by consensus.', 'timeFrame': 'at least two years, until end of follow-up'}

Please estimate the sample size based on the assumption: 
Randomized 1:1, followed for 2 years, significance level of 0.05, 90% power, and accounting for deviations in treatment allocation and death.
Sample size
        Based on previous studies, estimated event rates are 1.2% vs. 3.0% per year for patients with and without LAA closure, respectively [8, 9, 11, 16, 18, 19]. A total of 1302 patients need to be included if they are randomized 1:1, followed for 2Â years, and a significance level of 0.05 and 90% power is to be achieved. With these numbers, 16 primary events are expected for patients with LAA closure and 39 for patients with an open LAA. The trial will enroll 1500 patients to account for deviations in treatment allocation and death. Please see the trial protocol for more details [20].