Small Intestinal Bacterial Overgrowth Linked to Poor Outcomes in Patients With Heart Failure

Computer illustration of the human digestive system and a close-up view of bacteria found in the intestines.
Investigators sought to determine the prevalence of small intestinal bacterial overgrowth and establish its prognostic value in patients with heart failure.

Small intestinal bacterial overgrowth (SIBO) increases the risk for heart failure (HF) rehospitalization in patients with heart failure with reduced ejection fraction (HFrEF), as well as the risk for cardiovascular (CV) death in persons with heart failure with preserved ejection fraction (HFpEF), according to study results published in the Journal of the American Heart Association.

Researchers sought to assess the prevalence of SIBO and its potential for predicting adverse outcomes in hospitalized patients with different types of HF. The study prospectively enrolled patients who were hospitalized from July 2017 to May 2019. A composite of CV death and HF rehospitalization was the primary endpoint.

The analysis included patients who were tested for SIBO with use of the lactulose hydrogen-methane breath test. Patients who met ≥1 of the following criteria were considered SIBO-positive:

  • Fasting hydrogen level ≥20 ppm or a ≥20-ppm increase in hydrogen by 90 minutes was considered SIBO (H2)-positive
  • Methane levels ≥10 ppm at any test point were considered SIBO (CH4)-positive

From the total cohort of 287 patients who were tested for SIBO, 128 tested positive (mean age, 58.3±15 years; 73% male), and 159 were negative (mean age, 56.5±14.1 years; 79% male). Among persons with HFrEF, 78/189 (41%) tested positive for SIBO, and 50/98 (51%) with HFpEF tested positive for SIBO (P =.115).

Patients with HFrEF who were SIBO-positive had an increased risk for HF rehospitalization (hazard ratio [HR] 2.77 [95% CI, 1.62-4.74]; P <.001), and no difference was observed in CV death (HR 1.66 [95% CI, 0.4-6.94]; P =.467). SIBO-positive patients with HFpEF had an increased risk for CV death (HR 7.34 [95% CI, 1.58-34.13]; P =.011) compared with HF rehospitalization (HR 3.03 [95% CI, 0.98-9.38]; P =.077).

Univariate Cox regression analysis demonstrated that SIBO was associated with risk for the primary endpoint (HR 2.91 [95% CI, 1.81-4.68]; P < .001). After adjusting for variables, including body mass index, New York Heart Association III-IV class, use of β-blockers and aldosterone antagonists, and others, the investigators found that SIBO independently correlated with the primary endpoint in all patients with HF (adjusted HR 2.13 [95% CI, 1.26-3.58]; P =.005).

SIBO (CH4) had significant prognostic value regarding the study’s primary endpoint (HR 2.35 [95% CI, 1.38-4.02]; P <.001), and that association remained after adjustment (HR 2.19 [95% CI, 1.39-3.48]; P =.001). Patients with SIBO (H2 and CH4) had similar outcomes to patients with SIBO (H2) or SIBO (CH4) and had a higher risk for the primary endpoint compared with patients without SIBO.

The researchers noted several limitations to their findings, including the small sample size from a single center. Also, the hydrogen-methane breath test is not the gold standard for SIBO diagnosis, and age- and sex-matched control participants were not included.

“SIBO (CH4) may have a better prognostic value than SIBO (H2),” stated the study authors. “Given the high prevalence and prognostic correlation of SIBO in patients with HF, proactive treatment for patients with HF and SIBO may improve the prognosis and quality of life.”


Song Y, Liu Y, Qi B, et al. Association of small intestinal bacterial overgrowth with heart failure and its prediction for short-term outcomes. J Am Heart Assoc. 2021;10(7):e015292. doi:10.1161/JAHA.119.015292

This article originally appeared on The Cardiology Advisor