The goal of this clinical trial is to assess whether a peri-operative intervention with nutritional immune modulating intervention (Ensure Surgery Immunonutrition shake) has beneficial effects on the complex interplay between gut microbiome, systemic inflammation and malnutrition that is commonly present in advanced heart failure and the adverse events associated with left ventricular assist device (LVAD) placement in hospitalized advanced heart failure patients awaiting LVAD implantation. The main questions it aims to answer are: * Will pre-surgical supplementation with Ensure Surgery affect gut microbial composition and levels of inflammation among heart failure patients undergoing LVAD implantation? * Will pre-surgical supplementation with Ensure Surgery affect post-surgical morbidity (e.g., infections, intensive care unit length of stay (LOS)) and mortality? Participants will be evaluated for malnutrition and will be given Ensure Surgery Immunonutrition shake to drink in the days preceding their LVAD surgery. Blood and stool samples will be collected at prespecified timepoints before and after surgery. Researchers will compare malnourished participants drinking Ensure Surgery 3/day with well-nourished participants randomized to drink either 1/day or 3/day to see if any of the above supplementation strategies change the gut microbial composition, levels of inflammation, and post-surgical morbidity and mortality.