Impact of Transcatheter Aortic Valve Implantation (TAVI) on the Gut Microbiota in Patients With Aortic Valve Stenosis

Hypothesis The interaction between transcatheter aortic valve implantation (TAVI) and the gut microbiota represents an emerging field of investigation with potential clinical implications. Beyond restoring haemodynamic function, TAVI may influence the composition and function of the gut microbiome through several mechanisms. Improved cardiac output following TAVI enhances splanchnic perfusion, potentially reducing mucosal oedema and congestion, which may restore intestinal permeability and lead to favourable changes in microbiome composition.

Study Objective To evaluate changes in the gut microbiota following TAVI in patients with severe aortic valve stenosis.

Study Timeline and Data Collection Phase 1: Screening and Baseline Data Collection (1 month to 24 hours before TAVI, T1) Participants will be assessed for eligibility based on inclusion/exclusion criteria. Informed consent will be obtained, and participants will agree to telephone follow-up.

Collected data will include:

* Demographics and anthropometrics: sex, age, weight, height, BMI * Social history: smoking, alcohol, substance use * Medical history: comorbidities including hypertension, diabetes, dyslipidaemia, vascular disease, heart failure, stroke, TIA, embolism, PE * Echocardiography parameters * Venous Blood Sample (T1):

Collected up to 24 hours before TAVI for the following markers: TMAO, Complete blood count, Liver enzymes (SGOT, SGPT, ALP, γ-GT), Renal function (urea, creatinine), Electrolytes (K⁺, Na⁺, Ca²⁺, Mg²⁺), NT-proBNP, hsCRP, eGFR using the Cockcroft-Gault equation.

\- Stool Sample \& Dietary Assessment (T1): Participants will collect a stool sample using a standardised kit for 16S rRNA sequencing. A food frequency questionnaire will be completed to account for dietary influences on microbiota. This questionnaire will be repeated at each sample collection.

Sample Collection Procedure:

Participants will follow hygiene protocols and use provided containers for stool collection. Samples will be labeled with study ID, sample sequence (A or B), date of collection, and procedure type, and will be returned to the hospital promptly. No identifiable information will be recorded on the specimen.

Phase 2: Follow-Up (3-4 months after TAVI, T2) All assessments will be repeated 3 months post-procedure. If antibiotics were taken within this period, the follow-up assessment will be delayed by 1 month (i.e., 4 months post-TAVI).

Timepoint Comparisons:

T1 vs T2: Assess the impact of TAVI on gut microbiota.

• Change in serum trimethylamine N-oxide (TMAO) levels [Срок оценки: 3 months post TAVI]
• Correlation of microbiota changes with severity of aortic stenosis at baseline [Срок оценки: 3 months post TAVI]
• Correlation of microbiota changes with haemodynamic parameters [Срок оценки: 3 months post TAVI]