Gut Microbiome Profiling in Patients With Chronic Heart Failure

A map of gut microbiome compositional and functional features associated with a composite clinical outcome of advanced heart failure (composite of needing heart transplantation (including active listing), left ventricular assist device implantation, transition to hospice, or death) that occurs within 24 months of baseline visit. Fecal samples will be collected every 3 months over the first 12 month period. Microbiota composition will be determined by shotgun metagenomic sequencing, with taxonomic and metabolic pathway signatures generated using bioinformatic pipelines, respectively. Comprehensive microbiome signatures will encompass alpha and beta diversity, and differential abundance analysis.

Longitudinal changes in the gut microbiome composition and functionality in chronic heart failure will be determined. Microbiome signatures will be mapped from fecal samples collected every 3 months over a 12 month period, generated from shotgun metagenomic sequencing data and after processing through bioinformatic pipelines.

Changes in the host (human) metabolome profile in chronic heart failure with reduced ejection fraction will be determined. Participants provide fasting blood samples every 3 months for 12 months, from which plasma samples are prepared. Plasma metabolites are run through liquid chromatography-mass spectrometry (LC-MS) columns. MetID (Metabolite Identification from a reference database) and our LC-MS data are used to identify hundreds of metabolites with confidence levels 1-2. Many of the identified metabolites are gut microbiome-derived.

Changes in the host (human) cytokines in chronic heart failure with reduced ejection fraction will be determined. Participants provide fasting blood samples every 3 months for 12 months, from which serum samples are prepared. Cytokines are profiled using a 76-cytokine Luminex profiling system at the Stanford Human Immune Monitoring Center. This involves attaching antibodies specific to cytokines to beads using a capture molecule. The fluorescent molecules are attached to the cytokines, and fluorescence is used as the measure of cytokine abundance.

Participants' functional status (as measured by NYHA class, which ranges from 1 to 4, with 1 being no to minimal symptoms with activity, and 4 being symptoms at rest) will be assessed at each study visit for the first 12 months (every 3 months).

Participant self-reported functional status will be assessed via Kansas City Cardiomyopathy Questionnaire-12, which participant will complete at each study visit (every 3 months for 12 months). Overall summary and clinical summary scores (each 0-100, with 0 corresponding to severe and 100 corresponding to no functional limitations) will be calculated and compared over visits.