Hemodynamic effects of blood clots trapped by an inferior vena cava filter Josep M. López* 1 | Gerard Fortuny 1 | Dolors Puigjaner 1 | Joan Herrero 2 | Francesc Marimon 3 1 Departament d’ Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili. Tarragona, Catalunya, Spain 2 Departament d’ Enginyeria Química, Universitat Rovira i Virgili. Tarragona, Catalunya, Spain 3 Departament de Medicina i Cirurgia, Universitat Rovira i Virgili, Hospital Sant Joan, Reus, Catalunya, Spain Correspondence *Josep M. López, Departament d’ Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Av Països Catalans 26, Tarragona, Catalunya, Spain. Email: josep.m.lopez@urv.cat Summary The alteration of blood flow around an OPTEASE R  inferior vena cava filter with one or two blood clots attached was investigated by means of computational fluid dynamics. We used a patient–specific vein wall geometry, and we generated differ- ent clot models with shapes adapted to the filter and vein wall geometries. A total of eight geometries, with one or two clots and a total clot volume of 0.5 or 1 cm 3 , were considered. A non–Newtonian model for blood viscosity was adopted and the possible development of turbulence was accounted for by means of a three–equation model. Two blood flow rates were considered for each case, representative for rest and exercise conditions. In exercise conditions, flow unsteadiness and even turbu- lence was detected in some cases. Pressure and wall shear stress (WSS) distributions were modified in all cases. Clots attached to the filter downstream basket consider- ably increased averaged WSS values by up to almost 50%. In all the cases a flow recirculation region appeared downstream of the clot. The degree of flow stagnation in these regions, an indicator of propensity to thrombogenesis, was estimated in terms of mean residence times and mean blood viscosity. High levels of flow stagnation were detected in rest conditions in the wake of those clots that were placed upstream from the filter. Our results suggest that one downstream placed big clot, showing a higher tendency to induce flow instabilities and turbulence, might be more harmful than two small clots placed in tandem. KEYWORDS: Inferior vena cava filters, Computational fluid dynamics, Wall shear stress, Hemodynamics, Blood clot 1 INTRODUCTION Pulmonary embolism (PE) is a severe disease that can be life-threatening if left untreated. It occurs when blood flow in the pulmonary vascular system is partially blocked. In most cases, PE is caused by thrombi (blood clots) that migrate from deep veins in the legs and become lodged in the pulmonary vessels. Reports conducted in several countries in the last decade revealed that PE incidence was within the range of 0.5−1.1 per 1000 persons–year 1–4 . The standard treatment for PE, the administration of anticoagulant drugs 5 , is complemented under certain circumstances with the implantation of a filter in the inferior vena cava (IVC) 6–8 . IVC filters are metal devices created to help in the prevention of PE by capturing thrombi that are traveling with the blood flow and could therefore reach the pulmonary vessels. The efficacy of IVC filter implantation as a therapy is disputed. A clinical study made on a large basis of 1200 patients suggested the convenience of IVC filter placement in those DVT patients This article is protected by copyright. All rights reserved. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/cnm.3343