TFRC and Shock: To maximise the identification of relevant reports and reduce loss of information, a systematic search of the literature will be performed from inception until January 2025 using the terms “iron deficiency” as well as “iron”, “ferritin”, “transferrin”, “transferrin saturation”, “hepcidin” and “soluble transferrin receptor” matching these terms with the keywords “cardiogenic shock”, “acute heart failure”, “advanced heart failure”, “decompensated heart failure”, “lvad”, “left ventricular assist device”, “mechanical circulatory support”, “VA-ECMO” and “Extracorporeal Life Support”.