Description of the study populations
For each analytical population, patient selection process was represented by a flow diagram, and characteristics at inclusion were described as percentage for categorical variables, median with interquartile range (IQR), or mean with standard deviation (SD) for continuous variables, as appropriate. Characteristics were stratified according to whether levosimendan was administered for weaning from ECMO. The two groups were compared using adequate tests according to the type of variables and their distribution (Chi2 tests, Fisher’s exact tests, Wilcoxon's rank sum tests, or two-sample t tests).