Revisiting the Open Vein Hypothesis to Reduce the Postthrombotic Syndrome: Implications for Multidisciplinary Care and Research: A Scientific Statement From the American Heart Association

The "open vein hypothesis" postulates that early thrombus clearance and restoration of venous blood flow may prevent postthrombotic syndrome after proximal deep vein thrombosis. Since its proposal several decades ago, new insights from basic and clinical studies have motivated a re-evaluation and refinement of this hypothesis. According to data from these studies, susceptibility to postthrombotic syndrome occurs as a result of differences in genetic composition, thrombophilic conditions, predilection to inflammation and fibrosis, endogenous fibrinolytic capability, timing of symptom presentation and treatment initiation, and efficacy of antithrombotic therapy. Although initial restoration of an open vein appears to be beneficial for selected patient groups, freedom from postthrombotic syndrome is more likely in the setting of long-term venous patency, reduced recurrent thrombotic episodes, and reduced perithrombotic (eg, vein wall and valve) inflammation. These underlying biological mechanisms need further elucidation, with a long-term goal of personalizing treatment by mapping the individuals' clinical presentation with their underlying risk factors and assessing time-dependent biological processes that occur as a clinical venous thrombosis resolves. This scientific statement (1) highlights historical fundamentals of the open vein hypothesis and then showcases new research insights into the pathophysiological factors driving postthrombotic syndrome; (2) discusses advantages and disadvantages of imaging modalities for deep vein thrombosis used in clinical practice, including the potential to depict thrombus chronicity and status of vein wall injury; (3) proposes measures to develop integrated multidisciplinary care for deep vein thrombosis focused on the reduction of postthrombotic syndrome; and (4) identifies priority areas and questions for further research.