Intimal hyperplasia producing thrombus organization in an experimental venous thrombosis model

Abstract

A venous thrombosis animal model demonstrated similarities between intimal hyperplasia and thrombus organization. This has prompted the evaluation of a hypothesis that intimal hyperplasia may be the mechanism for thrombus organization in veins with normal pressure.Methods: Thrombi were produced in surgically exposed jugular veins of anesthetized, 18 to 20 kg pigs. Thrombosis was induced by a combination of devascularization, electric injury produced by a low amperage, direct current, and permanent partial ligation (50% diameter reduction). Vein segments were harvested at 0, 1,2, 7, 14, and 60 days and histologically examined for fibrin, red blood cells, platelets, smooth muscle cells, endothelial cells, elastic fibers, and collagen deposits. Results: Forty vein segments in 20 pigs were evaluated. Luminal thrombi with thickened walls developed in all specimens. All luminal thrombi demonstrated partial spontaneous thrombolysis over the period of observation. Intimal thickening consisting primarily of smooth muscle cells by day 2 was apparent and progressed until about 2 weeks, when collagen deposits became prominent within the neointima. The neointima frequently comprised half the cross-sectional area of the veins. Endothelial cells were present in the intima as single cells or as lining for clefts formed within the thickened intima. Conclusions: Smooth muscle cell proliferation with collagen deposition characteristic of intimal hyperplasia seemed to be the mechanism of thrombus organization in the experimental thrombosis model used in this study in which extensive stimulation was used to produce thrombosis.

Antenatal renal vein thrombosis after accidental electric shock in a pregnant woman.

“…As in our case, secondary visceral lesions arising from the initial neurovascular thermal injury may appear only at a later date. Descriptions of similar cases in adults as well as research studies on electrically induced venous thrombosis 13 provide additional support for our hypothesis. However, the link between RVT and fetal distress remains, for the time being, unclear.…”

Trombectomia com cateter de Fogarty no tratamento da tromboflebite jugular experimental em eqüinos

“…Sigel et al (1994) observaram o espessamento da parede das veias jugulares de suínos, após a indução da trombose, sendo que no décimo quarto dia foi evidente a maior deposição de matriz extracelular, especialmente colágeno, na parede vascular. Os mesmos autores sugerem que o enrijecimento da parede vascular somente ocorre quando a metodologia aplicada na indução dos trombos apresenta um estímulo trombogênico extenso.…”

“…A tríade de Virchow serve de base em estudos para a indução da trombose, em que a alteração na parede vascular pode ser obtida experimentalmente considerando-se o trauma causado por clampes (Underwood et al 1993), lesão química do endotélio (Silveira et al 2001), lesão endotelial térmica através do laser (Imbault et al 1996), aplicação de corrente elétrica (Sigel et al 1994), substituição de um segmento venoso por um segmento sintético (Van Zyl et al 2000) ou, ainda, na substituição por segmentos homólogos antigênicos (Hupkens & Cooley 1997).…”

“…Em estudos, nem sempre é possível se utilizar a espécie de interesse clíni-co. As espécies mais utilizadas para experimentação, em cirurgia vascular, são cães coelhos, ratos, suínos, primatas e humanos (Sigel et al 1994, Quarmby et al 1996, Van Zyl et al 2000, Silveira et al 2001, não existindo um modelo experimental para estudo da trombose nos eqüi-nos. Além de conhecer os mecanismos de evolução dos trombos, os modelos experimentais buscam testar os métodos terapêuticos existentes.…”

Catheter-Related Sheaths (CRS): Pathophysiology and Treatment Strategies

“…This thrombus subsequently underwent organization and resulted in vein wall thickening and intimal hyperplasia. The organization of intravascular thrombus involves an infiltration by smooth muscle cells and the development of a vascularized connective tissue that includes collagen, smooth muscle cells, and endothelial cells [22,23]. Inflammatory cells are also known to be involved in venous thrombosis [24].…”