In situ Pulmonary Artery Thrombosis: A Previously Overlooked Disease

Figures

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  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.

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  FIGURE 2. The risk factors of and pathogenic mechanism underlying CTEPH. The pathological conditions, including genetic mutation, inflammation-associating endothelial dysfunction, recurrent thrombosis, and reduced thrombolytic activity, result in the imbalance between thrombosis and thrombolysis, which causes insolubility and organization of the thrombi in pulmonary arteries. As the thrombi block the pulmonary arteries, the pulmonary circulation is diverted to the unblocked ones, where intravascular pressure and shear stress is consequently elevated. Both the thrombus-mediated blockade of pulmonary arteries and the diverted blood-mediated elevation in mechanical stress lead to vascular remodeling, increased pulmonary vascular resistance, progressive PH. CTEPH, chronic thromboembolic pulmonary hypertension; PTE, pulmonary thromboembolism; PH, pulmonary hypertension.

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  FIGURE 3. The coagulation cascade activated following pulmonary vascular endothelial cell injury. The pulmonary vascular hypoxic and inflammatory scenario leads to the following events: 1) endothelial cell injury and upregulates TF expression on monocytes; 2) the injuried endothelial cells promote platelets to release P-selectin, which further increases TF production; 3) the endothelial cells per se release P-selectin, which adheres to platelets and leukocytes, facilitating their deposition onto the endothelia; 4) the increased production of TF enhances thrombin production, which promotes conversion of fibrinogen to fibrin; 5) the deposited leukocytes and platelets are entangled with fibrin, leading to in situ pulmonary thrombosis. TF, tissue factor; WPb, Weibel-Palade bodies; PSGL-1, P-selectin glycoprotein ligand 1.