Venous thromboembolism and arterial thromboembolism. Many similarities, far beyond thrombosis per se.

Thromb Haemost 2008; 100: 181–183 Venous and arterial thromboembolic disorders are usually considered as two distinct disease entities.At first this belief appears to be indisputable. Arterial thrombi consist mainly of platelets and are induced by arterial plaque ruptures which tend to occur at sites where shear rates are high. Conversely, venous thrombi mainly consist of red blood cells and fibrin and tend to occur at sites where the vein wall is often normal, but blood flow and shear rates are low (1). Furthermore, major, known risk factors for arterial thrombosis (e.g. tobacco smoking, arterial hypertension, diabetes, and dyslipidemia) are completely different from risk factors that are known to provoke venous thrombosis, such as trauma, surgery and cancer. However, mechanisms beyond the development of venous and arterial thrombi are far more complex and certainly have more links, such as endothelial dysfunction and inflammation. Moreover, there also remains much to be understood about risk factors of venous thrombosis, given that currently as many as 26% to 47% of all venous thromboembolic events remain classified as “unprovoked” or “idiopathic” (2).