FIGURE 1.

The risk factors of PTE associated with DVT and in situ PAT. In the majority of cases, the systemic susceptible conditions, such as genetic mutations, endocrine disorders, and surgery, as well as the local conditions, such as anatomical and hemodynamic characteristics and trauma, elicit thrombus formation at the venous valves in lower extremities. After shedding from the venous valves, the thrombus travels through circulation to block either the main body or branches of pulmonary artery, leading to the PTE associated with DVT (arrows in dark red). On the other hand, pulmonary diseases, lung damage, and immunological, congenital, and hematological systemic diseases may cause in situ PAT (arrow in dark green). It is also possible that in situ PAT is formed under the susceptible systemic conditions of DVT, however, direct evidence is lacking (arrow in dark red dotted lines). PTE, pulmonary thromboembolism; DVT, deep vein thrombosis; in situ PAT, in situ pulmonary artery thrombosis.