PB0620 - Low molecular weight heparin slows the formation of clots from patients within twenty-four hours of acute PE

Background: Pulmonary embolism (PE) is a major cause of mortality and anticoagulation treatment with low molecular weight heparin (LMWH) is aimed at preventing short-term recurrence. Eliciting differences in clot properties may facilitate a better understanding of the mechanisms underlying LMWH treatment in PE patients.

Aims: To investigate formation and lysis of paired plasma clots from patients with acute PE and 24 hours after initial treatment with LMWH.

Methods: Paired patient samples were used to determine plasma clot characteristics (n=47). Clot formation and fibrinolysis was determined by turbidity (n=44). Fully formed clot structural comparisons were determined using laser scanning confocal microscopy. Statistical evaluation included paired t-test and the Wilcoxon signed-rank test.

Results: Clots formed from plasma samples taken 24 h after treatment with LMWH had a longer lag phase and time to maximum absorbance in comparison to those formed prior to treatment. No structural differences in fully formed clots were observed using confocal microscopy following LMWH treatment compared to pre-treatment samples.

Conclusion(s): LMWH changed clot formation and structure, which is in keeping with its anticoagulant mechanism of action. Lag time could be clinically important in future risk stratification studies alongside other prothrombotic properties to predict PE recurrence in patients receiving anticoagulation therapy. Predicting recurrence during anticoagulation would allow for personalization of treatment for each patient.