Prognostic value of elevated levels of intestinal microbe-generated metabolite trimethylamine-N-oxide in patients with heart failure: refining the gut hypothesis.

BACKGROUND: Altered intestinal function is prevalent in patients with heart failure (HF), but its role in adverse outcomes is unclear.
OBJECTIVES: This study investigated the potential pathophysiological contributions of intestinal microbiota in HF.
METHODS: We examined the relationship between fasting plasma trimethylamine-N-oxide (TMAO) and all-cause mortality over a 5-year follow-up in 720 patients with stable HF.
RESULTS: The median TMAO level was 5.0 μM, which was higher than in subjects without HF (3.5 μM; p < 0.001). There was modest but significant correlation between TMAO concentrations and B-type natriuretic peptide (BNP) levels (r = 0.23; p < 0.001). Higher plasma TMAO levels were associated with a 3.4-fold increased mortality risk. Following adjustments for traditional risk factors and BNP levels, elevated TMAO levels remained predictive of 5-year mortality risk (hazard ratio [HR]: 2.2; 95% CI: 1.42 to 3.43; p < 0.001), as well as following the addition of estimated glomerular filtration rate to the model (HR: 1.75; 95% CI: 1.07 to 2.86; p < 0.001).
CONCLUSIONS: High TMAO levels were observed in patients with HF, and elevated TMAO levels portended higher long-term mortality risk independent of traditional risk factors and cardiorenal indexes.