Microbiota has been associated with risk factors for cardiovascular diseases (hypertension, obesity, dyslipidemia, diabetes mellitus, heart failure). In animal models, the gut microbiota produces pro-inflammatory proteoglycans that increase the extent of myocardial infarction, reduced by treatment with probiotics (Lactobacillus). TMAO, a blood metabolite directly dependent on the gut microbiota is related to atherosclerotic plaque instability and major adverse cardiovascular events (MACE) in humans. Recent data demonstrate that blood levels of TMAO directly correlate with the risk of major MACE and mortality in patients with peripheral arterial disease (PAD).

The goal of this observational study is to evaluate the association between gut microbiota and TMAO serum levels and MACE and major adverse limb events (MALE) in patients with PAD and chronic limb threatening ischemia (CLTI) requiring a procedure of endovascular revascularization.

The main questions it aims to answer are:

• association between gut microbiota and TMAO serum levels and MALE after lower extremity revascularization.
• association between gut microbiota and TMAO serum levels and MACE after lower extremity revascularization.

Patients with CLTI requiring lower extremity endovascular revascularization will undergo stool sampling for determination of gut microbiota and blood sampling for the dosage of circulating TMAO before the endovascular procedure.

Incidence of MALE and MACE will be collected in a 24-months follow-up and will be associated with gut microbiota and TMAO serum levels.

Inclusion Criteria:

• age of at least 18 years
• Ankle/Brachial Index (ABI) of less than 80
• at least one lower limb stenosis greater than 50% documented by Ultrasound Color Doppler (US)
• stage 4 or 5 PAD diagnosis according to the Rutherford classification
• presence of chronic limb-threatening ischemia
• indication for LER of the target arterial stenosis

Exclusion Criteria:

• acute infections at present or in the previous month
• antibiotic treatment in the previous month
• primary hyperparathyroidism
• revascularization of the lower limb in the previous 3 months
• diabetic foot ulcers with signs of active infection or osteomyelitis
• organ transplantation
• active cancer
• liver disease at functional status B or C according to Child-Pugh
• absolute contraindication to antiplatelet therapy
• thrombophilia
• contraindication to endovascular revascularization

We will enroll consecutive subjects with PAD and CLTI requiring for endovascular revascularization and admitted to Internal Medicine Cardiovascular Unit of the Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma.