Heart failure (HF) is a syndrome with global clinical and socioeconomic burden worldwide owing to its poor prognosis. Accumulating evidence has implicated the possible contribution of gut microbiota-derived metabolites, short-chain fatty acids (SCFAs), on the pathology of a variety of diseases. The changes of SCFA concentration were reported to be observed in various cardiovascular diseases including HF in experimental animals and humans. HF causes hypoperfusion and/or congestion in the gut, which may lead to lowered production of SCFAs, possibly through the pathological changes of the gut microenvironment including microbiota composition. Recent studies suggest that SCFAs may play a significant role in the pathology of HF, possibly through an agonistic effect on G-protein-coupled receptors, histone deacetylases (HDACs) inhibition, restoration of mitochondrial function, amelioration of cardiac inflammatory response, its utilization as an energy source, and remote effect attributable to a protective effect on the other organs. Collectively, in the pathology of HF, SCFAs might play a significant role as a key mediator in the gut–heart axis. However, these possible mechanisms have not been entirely clarified and need further investigation.

Venous thromboembolism (VTE) is a common comorbidity of cancer, often referred to as cancer-associated thrombosis (CAT). Even though its prevalence has been increasing, its clinical picture has not been thoroughly investigated. In this single-center retrospective observational study, 259 patients who were treated for pulmonary embolism (PE) between January 2015 and December 2020 were available for analysis. The patients were divided by the presence or absence of concomitant malignancy, and those with malignancy (N = 120, 46%) were further classified into active (N = 40, 15%) and inactive groups according to the treatment status of malignancy. In patients with malignancy, PE was more often diagnosed incidentally by computed tomography or D-dimer testing, and the proportion of massive PE was lower. Although D-dimer levels overall decreased after the initiation of anticoagulation therapy, concomitant malignancy was independently associated with higher D-dimer at discharge despite the lower severity of PE at onset. The patients with malignancy had a poor prognosis during post-discharge follow-up. Active malignancy was independently associated with major adverse cardiovascular events (MACE) and major bleeding. D-dimer at discharge was an independent predictor of mortality even after adjustment for malignancy. This study’s findings suggest that CAT-PE patients might have hypercoagulable states, which can potentially lead to a poorer prognosis.