Vascular Remodeling: Just Say NO!

“You are only as old as your endothelium”, as often stated by Paul M Vanhoutte, when opening his famous “Mechanisms of Vasodilation” meetings from 1980 onwards, highlights the importance of endothelium and the continuous process of vascular remodeling in many physiological and pathophysiological situations as embryogenesis, wound healing, tumor growth and ischemic disease. In chronic and acute cardiovascular occlusive disease, different types of vascular remodeling contribute to tissue repair and vascular growth. Firstly, collateral growth represents the expansive growth of preexisting vessels, forming collateral bridges between arterial networks. Secondly, neovascularization refers to vascular growth from a combination of three different mechanisms: vasculogenesis is the formation of blood vessels by endothelial progenitors while angiogenesis refers to capillary sprouting or intussusceptive growth and arteriogenesis to the subsequent stabilization of these new vascular structures by mural cells1. Distinct, but partially overlapping, cellular and molecular pathways drive collateral growth and neovascularization (Figure 1)2. Hypoxia is known to stimulate neovascularization in the setting of ischemia, whereas fluid shear stress (FSS) might be the most important trigger for initiation of collateral growth. Besides these specific initial triggers, all types of vascular remodeling share growth factors, chemokines, proteases, and inflammatory cells, which play different roles in promoting and refining these processes

Use of covered stent grafts as treatment of traumatic venous injury to the inferior vena cava and iliac veins: A systematic review

Objective: Venous injury to the inferior vena cava or iliac veins is rare but can result in high mortality rates. Traditional treatment by repair or ligation can be technically demanding. A relatively new treatment modality is the use of a covered stent to cover the venous defect. The aim of the present systematic review was to assess the techniques, results, and challenges of covered stent graft repair of traumatic injury to the inferior vena cava and iliac veins.Methods: The PubMed (Medline) and Embase databases were systematically searched up to September 2020 by two of us (R.R.S. and D.D.) independently for studies reporting on covered stenting of the inferior vena cava or iliac veins after traumatic or iatrogenic injury. A methodologic quality assessment was performed using the modified Newcastle-Ottawa scale. Data were extracted for the following parameters: first author, year of publication, study design, number of patients, type and diameter of the stent graft, hemostatic success, complications, mortality, postoperative medication, follow-up type and duration, and venous segment patency. The main outcome was clinical success of the intervention, defined as direct hemostasis, with control of hemorrhage, hemodynamic recovery, and absence of contrast extravasation.Results: From the initial search, which yielded 1884 records, a total of 28 studies were identified for analysis. All reports consisted of case reports, except for one retrospective cohort study and one case series. A total of 35 patients had been treated with various covered stent grafts, predominantly thoracic or abdominal aortic endografts. In all patients, the treatment was technically successful. The 30-day mortality rate for the entire series was 2.9%. Three perioperative complications were described: one immediate stent occlusion, one partial thrombosis, and one pulmonary embolism. Additional in-stent thrombus formation was seen during follow-up in three patients, leading to one stent graft occlusion (asymptomatic). The postoperative anticoagulation strategy was highly heterogeneous. The median follow-up was 3 months (range, 0.1-84 months). However, follow-up with imaging studies was not performed in all cases.Conclusions: In selected cases of injury to the inferior vena cava and iliac veins, covered stent grafts can be successful for urgent hemostasis with good short-term results. Data on long-term follow-up are very limited