Sample size: We calculated sample size on the basis of primary outcome. Assuming the participation of 30 centers (15 in each group), an intracluster correlation of 0.01, a rate of symptomatic thromboembolic events or severe haemorrhage of 5% in the current practice group, we need a sample of 16170 patients (8085 in each group) to detect a 1.5 percentage absolute difference between the 2 groups (3.5% in the intervention group) with a power of 80% and a significance level of 5%.