[Risk factors in chronic thromboembolic pulmonary hypertension]

Although preoccupation with chronic thromboembolic pulmonary hypertension (CTEPH) among the scientific community is constantly increasing, the pathogenesis of this disease has not been completely elucidated and factors predisposing to its development are not precisely known. Some patients may be genetically conditioned to develop CTEPH, but only a few fibrinogen mutations and an increase in the frequency of polymorphisms of human leukocyte antigens have been described. Hereditary coagulation defects are no more prevalent in patients with CTEPH than in controls, except for factor VIII and antiphospholipid antibodies. Some studies have analyzed differences in the expression of type 1 tissue plasminogen activator inhibitor in the thrombus of patients with CTEPH (compared with thrombi of acute pulmonary thromboembolism [PTE]) and suggest that thrombosis in situ can contribute to the persistence of the coagulum and disease progression. Some characteristics of acute PTE have been associated with its progression to CTEPH, such as idiopathic PTE, large perfusion defects, massive PTE, recurrent PTE and pulmonary hypertension persisting at 5 weeks after the thrombotic event. Several clinical factors that increase the risk of CTEPH have been described, such as splenectomy, ventricular shunts, and chronic inflammatory diseases. Thyroid replacement therapy and cancer have also emerged as new predictors of CTEPH. Identification of new predisposing factors will provide clues to the pathogenic mechanisms of the disease and will facilitate early diagnosis and more effective treatment.