Assessment of heterogeneity.

We assessed heterogeneity by inspecting the graphs and use of χ², p value, and I² statistics. We considered a p value of less than 0.10 as significant. We interpreted I² value of 50% or greater as high heterogeneity. In case of heterogeneity, we investigated the reason. The main predefined reasons for investigating heterogeneity were (1) hemorrhage vs rehemorrhage, (2) before and after 2 years of rehemorrhage, (3) location of CMs, and (4) type of calculation. See the supplemental material for heterogeneity and bias assessment.