*4.1. Gut Microbiota and Heart Failure*

Heart failure (HF) is a serious health problem that negatively affects mortality and morbidity worldwide [82]. The levels of several proinflammatory cytokines in plasma are correlated with the severity and prognosis of the disease in patients with heart failure, who are thought to experience a persistent systemic inflammatory response [83,84]. The gut is a blood-demanding organ, and because of its restricted blood supply, the villi (and microvilli) are vulnerable to functional ischemia. A drop in the pH of the intestinal mucosa can result in intestinal ischemia in patients with HF [85]. A decline in intestinal mucosal pH is an indicator of intestinal ischemia in patients with HF [86]. Gut microbiota composition and metabolic parameters of patients with chronic heart failure (CHF) were significantly different from those of the control group, according to a fecal metagenomic study of 53 patients with chronic heart failure and 41 control participants [87]. Patients with HF are almost invariably found to have impaired intestinal barriers [88]. *Yersinia enterocolitica*, *Candida*, *Campylobacter*, *Salmonella*, *Shigella*, and other pathogenic bacteria are more prevalent in patients with CHF than in healthy controls [89]. According to the NYHA scale, these changes are strongly associated with HF severity [89].
