**7. Natural history and complications**

Compared to lower extremity deep vein thrombosis, relatively little is known about the natural history of deep arm vein thrombosis. The follow-up of patients not receiving anticoagulant treatment was reviewed by Thomas & Zierler, who found high rates of postthrombotic syndrome (74%) and pulmonary embolism (12%) in patients treated only with physical methods (rest, heat, elevation) (Thomas & Zierler, 2005). These findings underscore the importance of a correct and fast diagnosis of upper extremity deep vein thrombosis and challenge the common view of arm vein thrombosis as a relatively harmless disease. However, even patients that are treated according to current guidelines have a significant risk of severe complications (Table 3). Compared to lower extremity deep vein thrombosis, patients with deep arm vein thrombosis present less frequently with concomitant pulmonary embolism (9% versus 30%) (Munoz et al*.*, 2008; Lechner et al*.*, 2008). However, pulmonary embolism caused by deep arm vein thrombosis can even be fatal in rare cases (Monreal et al*.*, 1994). With the exception of patients with malignancies, the recurrence rate tends to be lower than in deep vein thrombosis (Spencer et al*.*, 2007; Munoz et al*.*, 2008). However, the total mortality of patients with upper extremity and lower extremity thrombosis appears to be similar and is mainly related to the underlying disease (Spencer et al*.*, 2007; Munoz et al*.*, 2008). Contrary to common believe, post-thrombotic syndrome is not a rare complication in deep arm vein thrombosis and may lead to functional disability and significant impaired quality of life in these patients (Prandoni et al*.*, 2004; Kahn et al*.*, 2005; Vik et al*.*, 2009). Two modified versions of a validated score system for post-thrombotic syndrome in lower extremity thrombosis (Prandoni et al*.*, 1997b) have been adapted to arm vein thrombosis (Table 4).


Table 3. Common complications of deep arm vein thrombosis.
