Disease
Human Immunodeficiency Virus
Infection with human immunodeficiency virus has been associated with the development of pulmonary vascular diseases. The presence of pulmonary arterial hypertension associated with human immunodeficiency virus infection was first reported in 1987 in a patient with hemophilia with membrane proliferative glomerulonephritis (inflammation of the capillary loops in the kidney nephron). Subsequent reports in human immunodeficiency virus-infected hemophiliacs followed; then came reports of cases of pulmonary arterial hypertension in nonhemophiliacs, highlighting a direct association between pulmonary arterial hypertension and human immunodeficiency virus. The nature of the association between human immunodeficiency virus and pulmonary arterial hypertension remains unknown, but the medical community stresses the interaction between genetic and environmental factors. There appears to be no link to the stage of human immunodeficiency virus infection and the prevalence or severity of pulmonary arterial hypertension. In light of improvements in drug therapy for human immunodeficiency virus and the increasing prevalence of human immunodeficiency virus worldwide, the number of human immunodeficiency virus-related pulmonary arterial hypertension cases will likely increase.
Connective Tissue Diseases
pulmonary arterial hypertension has been linked with a range of connective tissue disease, including systemic sclerosis (scleroderma) and systemic lupus erythematosus. Associations have also been made between pulmonary arterial hypertension and rheumatoid arthritis, dermatopolymyositis, and primary Sjogren’s syndrome, but to a lesser extent. Within the population with connective tissue disease, pulmonary arterial hypertension is most frequently observed in patients with scleroderma-related disease, often referred to as CREST (calcinosis, Raynaud’s phenomenon, esophageal dysmotility, sclerodactyly [thickening or tightening of the skin], and telangiectasia [permanent dilation of the blood vessels causing small red lesions in the skin or mucosal membranes]) syndrome. Histopathological changes observed in this group are similar to those in pulmonary arterial hypertension, although there is often a greater degree of thickening of the adventitia (connective tissue covering).
Early studies using the echocardiogram to investigate the presence of pulmonary arterial hypertension estimated the incidence of pulmonary arterial hypertension in association with scleroderma at 30-50%. However, a new study involving 722 scleroderma patients performed right-heart catheterization (a more accurate assessment of the presence of pulmonary arterial hypertension) to determine the presence of pulmonary arterial hypertension, which the researchers identified in only 12% of patients. This value may be a more realistic marker. The mechanisms responsible for pulmonary arterial hypertension in patients with connective tissue disease remain unknown. An immunological mechanism has been suggested due to the presence of an anticentromere antibody, rheumatoid factor, immunoglobulin-G, and complement fragments (the complement system has an important role in the immune response). Patients with connective tissue disease and pulmonary arterial hypertension are primarily female and older (mean age of 66 years). They generally have a worse prognosis than pulmonary arterial hypertension patients because they tend to respond poorly to available pulmonary arterial hypertension therapies and they have underlying disease.
Portal Hypertension. An association between pulmonary arterial hypertension and hepatic dysfunction was first reported in 1951. The presence of portal hypertension resulting from hepatic abnormality rather than the hepatic disorder itself appears to be the key to the development of pulmonary arterial hypertension. pulmonary arterial hypertension associated with portal hypertension is also histopathologically similar to pulmonary arterial hypertension. The exact mechanism by which the presence of portal hypertension leads to the development of pulmonary arterial hypertension remains unknown. Researchers have suggested that the presence of a portal-systemic shunt (abnormal vascular connections between the hepatic vein and the systemic circulation) may facilitate the delivery of vasoconstrictors and inflammatory mediators, including 5-HT, into the pulmonary circulation; in healthy individuals, the vasoconstrictors and inflammatory mediators would be cleared by the liver. Liver transplant centers report the frequency of portopulmonary hypertension is 4-15%.
Congenital Heart Disease (Eisenmenger’s Syndrome). Pulmonary vascular disease due to the presence of an altered systemic-pulmonary connection such as an atrial septal defect, a ventricular septal defect, patent ductus arteriosis (failure of key fetal blood vessel to close after birth), or an aortopulmonary window (a hole between the main pulmonary artery and the aorta) is collectively referred to as Eisenmenger’s syndrome. pulmonary arterial hypertension resulting from Eisenmenger’s syndrome is histologically similar to pulmonary arterial hypertension. The condition generally occurs following a period of reduced pulmonary vascular resistance and high pulmonary blood flow that occurs after left-to-right shunt (movement of the blood from the left-heart circulation to the right-heart circulation). Morphologic changes occur in the pulmonary vessels, and when pulmonary vascular resistance exceeds systemic vascular resistance, the movement of blood reverses. The development of pulmonary arterial hypertension is related to the size and type of defect. Patients with pulmonary arterial hypertension associated with congenital heart disease generally have a better prognosis than do patients with pulmonary arterial hypertension.
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