Sample size is based on available results from the first GLUTAMICS study. In that study, the following increase of NT-proBNP from the preoperative value to third postoperative day (mean ± SD) were observed in patients with LVEF ≤ 0.30 or EuroSCORE II ≥ 3.0 undergoing coronary artery surgery for with or without concomitant procedure.