ABSTRACT
Venous thromboembolism (VTE) is a common event. It may be asymptomatic or lead to
pulmonary embolism (PE), which may be fatal. In the eighteenth and nineteenth centuries,
pulmonary arterial thrombosis was first recognized as an entity. While some attributed
death and causality to this finding on autopsy, others merely commented on it incidentally.
The fact that pulmonary arterial thrombosis may occur from a venous VTE, an extra-
pulmonary source, was not entertained. In 1858, Rudolf Virchow recognized that the
aforementioned phenomenon might occur from a pulmonary, or an extra-pulmonary
source. He stated the importance of thrombi in remote venous systems that may dislodge
and cause secondary occlusion such as PE. It is during this time that he postulated the
etiologies of deep vein thrombosis (DVT) and proposed what is today called “Virchow’s
triad” as follows: hypercoagulability, blood stasis, and vessel injury(1).
