In cardiogenic shock (CS), pathophysiological changes include microcirculatory dysfunction, vascular leakage, and an increase in platelet and leukocyte adhesion to the endothelium, as well as endothelial activation and dysfunction. The endothelial glycocalyx has been recognized as a central modulator of these processes. Glycosaminoglycan heparan sulfate is a major component of the glycocalyx of endothelial cells, and syndecan-1 (S1) represents the most prevalent proteoglycan. The aim of the current study was to investigate circulating levels of the glycocalyx components in patients with infarct-related CS. In 184 patients with CS complicating acute myocardial infarction, blood samples were collected at admission and after one day. Intra-aortic balloon pumping was used in 94 patients (51%). Glycosaminoglycan heparan sulfate and S1 were measured using standard enzyme-linked immunosorbent assay kits. All-cause mortality at 30 days was used for outcome assessment. Levels of S1 decreased between days 1 and 2 (339 [interquartile range [QR], 109-852] vs. 220 [IQR, 57-606] ng/mL; P = 0.01). In contrast, glycosaminoglycan heparan sulfate increased over time (1.9 [IQR, 0.3-6.4] vs. 7.1 [IQR, 3.7-11.7] mg/mL; P < 0.001). Survivors at 30 days had lower admission S1 levels (P < 0.001). In multivariable analysis, S1 remained an independent predictor of 30-day mortality (odds ratio per μg/mL, 2.2 [95% confidence interval, 1.30-3.58]; P = 0.003) together with serum lactate, age, and ejection fraction. Increased levels of S1 are an independent predictor of short-term mortality in patients with acute myocardial infarction and CS.ClinicalTrials.gov Identifier: NCT00491036.