Abstract
Arterial and venous thromboses are sustained by development of intraluminal thrombi,
respectively, within the venous and arterial systems. The composition and structure
of arterial and venous thrombi have been historically considered as being very different.
Arterial thrombi (conventionally defined as “white”) have been traditionally proposed
to be composed mainly of fibrin and platelet aggregates, whilst venous thrombi (conventionally
defined as “red”) have been proposed as mostly being enriched in fibrin and erythrocytes.
This archaic dichotomy seems ever more questionable, since it barely reflects the
pathophysiology of thrombus formation in vivo. Both types of thrombi are actually
composed of a complex fibrin network but, importantly, also contain essentially the
same blood-borne cells (i.e., red blood cells, leukocytes, and platelets), and it
is only the relative content of these individual elements that differ between venous
and arterial clots or, otherwise, between thrombi generated under different conditions
of blood flow and shear stress. Convincing evidence now suggests that either white
or red intracoronary thrombi may be present in patients with myocardial infarction
and, even more importantly, red thrombi may be more prone to distal embolization during
percutaneous coronary intervention than those with lower content of erythrocytes.
Conversely, it is now accepted that components traditionally considered to be involved
“only” in arterial thrombosis are also represented in venous thrombosis. Thus, platelets
comprise important components of venous clots, although they may be present in lower
amounts here than in arterial thrombi, and von Willebrand factor is also represented
in both arterial and venous thrombi. Of importance, such evidence thus supports the
concept that adjunctive treatment normally associated to prevention of arterial thrombosis
(e.g., aspirin) may have a role also in prevention and treatment of venous thrombosis.
Keywords
hemostasis - thrombosis - cardiovascular disease - venous thromboembolism - arterial
thrombosis - blood coagulation
