About this Research Topic
Pulmonary hypertension (PH), defined as a mean pulmonary arterial pressure (PAP) ≥ 25 mmHg at rest as assessed by right heart catheterization, is characterized by elevated pulmonary arterial pressure and increased pulmonary vascular resistance. In the classification of PH, 5 major categories of the disorder are classified, including (Group 1) pulmonary arterial hypertension (PAH), (Group 2) PH due to left heart disease, (Group 3) PH due to lung diseases and/or hypoxia, (Group 4) chronic thromboembolic pulmonary hypertension, and (Group 5) others.
Especially, Group 1, PAH, is caused by small pulmonary artery obstruction due to vascular proliferation and remodeling, in which the pathological changes in the pulmonary arteries in PAH include endothelial injury, proliferation and spasm of vascular smooth muscle cells (VSMC) and migration of inflammatory cells. Pulmonary veno-occlusive diseases and/or pulmonary capillary hemangiomatosis (Group 1) should be a distinct category but not completely separated from PAH as they share similar characteristics with idiopathic PAH (IPAH) but also demonstrate some differences.
Group 4, CTEPH, is caused by mechanical obstruction of pulmonary arteries due to residual pulmonary thromboembolism or in situ thrombosis, which may be initiated or aggravated by abnormalities in either the clotting cascade, endothelial cells, or platelets. Although inflammatory infiltrates are commonly detected in the pulmonary endarterectomy specimens, it remains unknown whether thrombosis or platelet dysfunction is a cause or rather a consequence of the disorder. It has been reported that the plasma levels of factor VIII or thrombin-activatable fibrinolysis inhibitor (TAFI) is elevated in patients with CTEPH. CTEPH is regarded as a consequence of pulmonary thromboembolism (PTE) due to venous thromboembolism (VTE). Thus, it is highly possible that the pathophysiology is different between PAH and CTEPH.
Although significant research progress has been made on the pathogenesis of PH, the detailed mechanisms of the disorder still remain to be elucidated. In the clinical situation, significant progress has also been made for both diagnosis and treatment; however, more effective and less invasive diagnostic and/or therapeutic tools should be developed.
In this Research Topic, the experts in the field are welcomed to write articles regarding the recent progress in their own fields. The Topic Editors are indebted to all authors for their considerable time and effort to create high-quality articles, and sincerely hopes that this Research Topic can be a great help in the management of PH, in terms of clinical classification, pathophysiology, genetics, diagnosis, and treatment.
Keywords: PAH, CTEPH, Mechanism, Diagnosis, Treatment
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