Deep venous free-floating thrombus: A review and meta-analysis

The main risk associated with deep vein thrombosis (DVT) is pulmonary embolism (PE). The risk of PE can be stratified, particularly based on the location of the DVT, i.e. proximal or distal. Another potentially embolic feature that has been reported is the presence of a free-floating thrombus (FFT). However, this phenomenon remains controversial and raises several unanswered questions.

We aimed to determine whether the presence of FFT has any clinical significance regarding the risk of pulmonary embolism.

We conducted a systematic literature review and a meta-analysis using the keywords "free-floating thrombus" and "pulmonary embolism" in the MEDLINE database.

A total of 35 publications were found to be relevant. The presence of FFT was associated with a higher risk of primary PE (77 vs. 23% in the absence of FFT; OR 3.3, 95% CI 1.4-7.7; P<0.02) and secondary PE (11 vs. 1.6% in the absence of FFT; OR 2.2, 95% CI 1.3-3.9; P<0.004). The incidence of secondary symptomatic PE was not statistically significant.

The free-floating characteristic of DVT is associated with a higher risk of initial PE at diagnosis and a higher risk of secondary PE, although it does not appear to be associated with an increased risk of secondary symptomatic PE. However, our meta-analysis lacks sufficient power to confirm this conclusion.