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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)

Figure 8-1.

Pulmonary arterial hypertensionpathophysiology. BMPR-2: bone morphogenetic protein receptor II; ALK1: activin receptor-like kinase 1; HTT: hydroxytryptamine transporter; ec-NOS: nitric oxide synthase; CPS: carbamyl phosphate synthase.

WHO Functional Classification of PAH

Table 8-1 WHO Functional Classification of Pulmonary Arterial Hypertension

Etiology of PAH

(Group 1 of WHO Pulmonary Hypertension Classification) (J Am Cardiol 2009;53:1573)

  • 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)


Dependent on WHO Functional Class, Hemodynamics, & Etiology of PAH

  • 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), evaluation for chronic thromboembolic ...

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