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- Clinical pathological definition: vasculopathy of the small pulmonary arteries which leads to ↑ pulmonary vascular resistance; may progress to right heart dysfunction & failure
- Hemodynamic definition: mean pulmonary artery pressure (mPAP) ≥25mmHg at rest, AND pulmonary capillary wedge pressure (PCWP) or left ventricular end-diastolic pressure (LVEDP) ≤15mmHg measured by right heart catheterization
- Established disease mediators: endothelin-1, prostacyclin, nitric oxide (J Am Cardiol 2009;53:1573)
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WHO Functional Classification of PAH
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(Group 1 of WHO Pulmonary Hypertension Classification) (J Am Cardiol 2009;53:1573)
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- Idiopathic (IPAH)
- Heritable (BMPR2, ALK1, endoglin, unknown)
- Drug or toxin-induced: fenfluramine, cocaine, toxic rapeseed oil
- Associated with (APAH): connective tissue diseases, HIV infection, portal hypertension, congenital heart diseases, schistosomiasis, chronic hemolytic anemia
- Persistent pulmonary hypertension of the newborn
- Pulmonary veno-occlusive disease (PVOD) &/or pulmonary capillary hemangiomatosis (PCH)
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Dependent on WHO Functional Class, Hemodynamics, & Etiology of PAH
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- Diagnosis made hemodynamically by right heart catheterization (RHC) (Circulation 2006;114;1417)
- Establishes diagnosis & guides treatment decisions
- Evaluates pulmonary vasoreactivity
- Use fast-acting, short-duration vasodilators (ex: epoprostenol, nitric oxide, adenosine) to determine extent of vasodilator response
- Positive response: reduction of mPAP by at least 10mmHg to a value of 40mmHg or less; ↑ or unchanged CO
- Negative response: should never receive trial of calcium channel blockers; move to PAH targeted therapy
- Echocardiography: assess right heart function & right-sided chamber size, estimate pulmonary pressures; used primarily as screening tool & helpful in ruling out other cardiac processes
- Evaluation of etiology of PAH: HIV test, serologies for connective tissue diseases, hepatitis panel, thyroid function tests, pulmonary function tests (to evaluate for restrictive or obstructive lung disease), ...