Histologic assessment of lower extremity deep vein thrombus from patients undergoing percutaneous mechanical...

Histologic analyses of deep vein thrombi (DVTs) have used autopsy samples and animal models. To the best of our knowledge, no previous study has reported on thrombus composition after percutaneous mechanical extraction. Because elements of chronicity and organization render thrombus resistant to anticoagulation and thrombolysis, a better understanding of clot evolution could inform therapy.

We performed a histologic evaluation of DVTs from consecutive patients who had undergone mechanical thrombectomy for extensive iliofemoral DVTs using the Clottriever/Flowtriever device (Inari Medical, Irvine, Calif). The DVTs were scored using a semiquantitative method according to the degree of fibrosis (collagen deposition on trichrome staining) and organization (endothelial growth with capillaries and fibroblastic penetration).

Twenty-three specimens were available for analysis, with 20 presenting as acute DVT (≤14 days from symptom onset). Of the 23 patients, 11 (48%) had had >5% fibrosis (ie, collagen deposition) and 14 (61%) had had >5% organization (ie, endothelial growth, capillaries, fibroblasts). Four patients with acute DVT had had ≥25% organized thrombus and two had had ≥25% collagen deposition. Of the 20 patients with acute DVT, 40% had had >5% fibrosis and 55% had had >5% organization. The acuity of DVT did not correlate with the amount of fibrosis or organizing scores.

A large proportion of patients with acute DVT will have histologic elements of chronicity and fibrosis. A better understanding of the relationship between such elements and the response to anticoagulant agents and fibrinolytic drugs could inform our approach to therapy.