CLDN1 and hydrops fetalis: In the entirety of patients with HF (pooled patients with HFrEF and HFpEF), the expression of occludin and claudin-1 in the intestinal mucosa (immunohistochemical semi-quantification) was significantly inversely correlated with endotoxin concentration (r = −0.376, p < 0.05 for occludin; and r = −0.446, p < 0.01 for claudin-1) (Figure 5).