Low-grade endotoxemia in acute pulmonary embolism: Links with prothrombotic plasma fibrin clot phenotype.

Background: Lipopolysaccharide (LPS) can traverse the intestinal barrier and enter bloodstream, causing endotoxemia and triggering inflammation. Increased circulating LPS was reported in arterial thromboembolism. We investigated whether increased LPS levels occur in acute pulmonary embolism (PE) and if it is associated with a prothrombotic state.

Methods: We studied 120 normotensive PE patients (aged 59 [48-68] years) on admission, after 5-7 days, and after a 3-month anticoagulation. Serum LPS levels, along with zonulin, a marker of gut permeability, endogenous thrombin potential (ETP), fibrin clot permeability (K), clot lysis time (CLT), fibrinolysis proteins, and platelet markers were assessed.

Results: Median LPS concentration on admission was 70.5 (61.5-82) pg/mL (min-max, 34-134 pg/mL), in association with C-reactive protein (r = 0.22, p = 0.018), but not with fibrinogen, D-dimer or platelet markers. Patients with more severe PE had higher LPS levels compared with the remainder. Median zonulin level was 3.26 (2.74-4.08) ng/mL and correlated with LPS (r = 0.66, p < 0.0001). Patients with baseline LPS levels in the top quartile (≥82 pg/mL; n = 29) compared to lower quartiles had 18.6 % increased ETP, 14.5 % reduced K, and 25.3 % prolonged CLT, related to higher plasminogen activator inhibitor type 1 (PAI-1) levels. LPS decreased by 23.4 % after 5-7 days and by 40.4 % after 3-month anticoagulation together with reduced zonulin by 18.4 % and 22.3 %, respectively, compared to baseline (all p < 0.001). LPS levels were not related with fibrin characteristics and other variables assessed at 3 months.

Conclusions: Low-grade endotoxemia is detectable in patients with acute PE and may contribute to increased thrombin generation and PAI-1-mediated hypofibrinolysis.