Pulmonary Arterial Hypertension
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- Pulmonary arterial hypertension (PAH) is a category of pulmonary hypertension (PH) characterized by abnormalities in the small pulmonary arteries (pre-capillary PH) that produce increased pulmonary arterial pressure (PAP) and vascular resistance, eventually resulting in right-sided heart failure. PAH is a progressive disorder associated with increased mortality:
- PAH is defined by (1):
- Mean PAP ≥25 mm Hg at rest
- Pulmonary capillary wedge pressure ≤15 mm Hg
- Classified as primary [without cause: Now idiopathic pulmonary arterial hypertension (IPAH)] or secondary [with cause or associated condition]
- Also classified into 5 main categories:
- Idiopathic: Sporadic, with no family history or risk factors
- Heritable: IPAH with mutations or familial cases with or without mutations
- Drug or toxin induced: Mostly associated with anorectics
- Associated: Connective tissue diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis, scleroderma); HIV infection; portal hypertension; congenital heart disease; schistosomiasis; chronic hemolytic anemia (e.g., sickle cell disease)
- Persistent PH of the newborn
- PAH is defined by (1):
- System(s) affected: Pulmonary; Cardiovascular
- Age: Can occur at any age; mean age, 37 years
- Sex (IPAH): Female > Male (~2:1)
- IPAH: Low, ~2–6 per million
- Drug-induced PAH: 1/25,000 with >3 months of anorectic use
- HIV associated: 0.5/100
- Portal hypertension associated: 1–6/100
- Scleroderma associated: 6–60%
- PAH: ~15–50 cases per million
- IPAH: ~6 cases per million
- Female sex
- Previous anorectic drug use
- Recent acute pulmonary embolism
- Commonly associated conditions
- 1st-degree relatives of patient with familial PAH
- 75% of heritable pulmonary arterial hypertension (HPAH) cases and 25% of IPAH cases have mutations in BMPR2 (autosomal dominant)
- Mutations in ALK1 and endoglin (autosomal dominant) also are associated with PAH.
- Pulmonary: Inflammation, vasoconstriction, endothelial dysfunction, and remodeling of pulmonary arteries produced by increased cell proliferation and reduced rates of apoptosis lead to obstruction.
- Cardiovascular: Right ventricular hypertrophy (RVH), eventually leading to right-sided heart failure
- IPAH: By definition, unknown. True IPAH is mostly sporadic or sometimes familial in nature.
- Pulmonary arteriolar hyperactivity and vasoconstriction, occult thromboembolism, or autoimmune (high frequency of antinuclear antibodies)
Commonly Associated Conditions
See Associated PAH, above.