Pulmonary Arterial Hypertension
Summary:
Pulmonary Arterial Hypertension (PAH) is a form of pre-capillary pulmonary hypertension (PH) defined by a mean pulmonary artery pressure (mPAP) > 20 mmHg, pulmonary capillary wedge pressure (PCWP) ≤ 15 mmHg, and pulmonary vascular resistance (PVR) ≥ 3 Woods units. PAH can be caused by various conditions, including idiopathic factors, genetic mutations, drug toxicity, and diseases such as connective tissue disease and HIV.
Causes (WHO Group 1 Classification):
1.1 Idiopathic
1.2 Heritable (e.g., BMPR2 mutation)
1.3 Drug or toxin-associated
1.4 Related to diseases like connective tissue disorders, HIV, portal hypertension, congenital heart disease, and schistosomiasis
1.5 Responsive to calcium channel blockers (CCBs)
1.6 Pulmonary veno-occlusive disease (PVOD)
Diagnostics:
- Basic labs (CBC, CMP, TFTs, HIV, ANA), with genetic testing when indicated.
- Imaging (EKG, CXR, TTE, high-resolution CT chest, V/Q scan).
- Right heart catheterization with vasodilator testing if needed.
- Functional tests like PFTs, 6-minute walk test, and overnight oximetry.
Initial Therapies:
- Treat underlying causes, use supplemental oxygen and diuretics.
- Calcium Channel Blockers (CCBs) for patients with a positive vasodilator response.
- Referral to a PH center of excellence is recommended.
Risk Stratification:
- Based on NYHA functional class, 6-minute walk test, right atrial pressure, and NT-proBNP levels to guide treatment decisions.
Special Considerations for Cardio-OB:
- PAH is associated with increased morbidity and mortality in pregnancy.
- Management includes contraception, multidisciplinary team care, planned delivery, and careful monitoring postpartum.
Therapeutic Pathways:
- Nitric oxide pathway: PDE5 inhibitors (sildenafil, tadalafil), soluble guanylate cyclase stimulators (riociguat).
- Endothelin-1 pathway: Endothelin receptor antagonists (macitentan, bosentan, ambrisentan – note teratogenic risks).
- Prostacyclin pathway: Includes epoprostenol, iloprost, treprostinil, and selexipag.
Surgical Therapies:
Options include bilateral lung transplantation, heart-lung transplantation, and balloon atrial septostomy.
Produced by: Dr. Juliette Power, Edited by Dr. G. Ramani and Dr. Karan Desai
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