Pulmonary Hypertension¶
Chapter 294 | Part 6: Cardiovascular Disorders
KEY CLINICAL POINTS¶
- Pulmonary hypertension (PH) is a heterogeneous disease characterized by increased pulmonary artery pressure and vascular resistance, leading to right heart failure.
- The 2018 World Symposium classification divides PH into five groups, with Group 1 (PAH) being the most common and associated with genetic mutations like BMPR2.
- Early diagnosis and multidisciplinary management are critical, with treatment options including endothelin receptor antagonists, PDE5 inhibitors, and prostacyclin analogs.
- Chronic thromboembolic pulmonary hypertension (CTEPH) is curable with pulmonary endarterectomy or balloon pulmonary angioplasty.
- Genetic testing and advanced imaging (e.g., right heart catheterization) are essential for accurate classification and guiding therapy.
1. DEFINITION & OVERVIEW¶
Pulmonary hypertension (PH) is defined as mean pulmonary artery pressure (mPAP) >20 mmHg at rest, with increased pulmonary vascular resistance (PVR). It encompasses a spectrum of diseases, including pulmonary arterial hypertension (PAH), left heart disease-related PH, and chronic thromboembolic pulmonary hypertension (CTEPH).
Table 294-1: World Symposium on Pulmonary Hypertension Clinical Classification¶
| GROUP | DESCRIPTION |
|---|---|
| GROUP 1 | Pulmonary arterial hypertension (PAH) |
| GROUP 2 | PH associated with left heart disease |
| GROUP 3 | PH associated with lung diseases/hypoxia |
| GROUP 4 | PH associated with pulmonary artery obstructions |
| GROUP 5 | PH with unclear/multifactorial mechanisms |
1.1 Pathophysiology¶
PH results from vascular remodeling, including medial hypertrophy, intimal fibrosis, and plexiform lesions. Genetic factors (e.g., BMPR2 mutations) and epigenetic changes (e.g., TET2/DNMT3B dysregulation) contribute to disease progression.
1.2 Clinical Impact¶
Untreated PH leads to right ventricular failure and high mortality. Early diagnosis is critical to improve outcomes, as delays in treatment can result in irreversible vascular remodeling.
2. EPIDEMIOLOGY¶
PH is underdiagnosed, with an estimated prevalence of 15-50 cases per 100,000. Risk factors include left heart disease, chronic lung disease, and genetic predispositions (e.g., BMPR2 mutations). Women are more commonly affected than men, though men have worse prognoses.
2.1 Incidence & Prevalence¶
PAH is rare, with an incidence of ~1-2 per million. CTEPH occurs in 1-3% of patients with prior pulmonary embolism. Left heart disease-related PH is more common, affecting ~10% of patients with heart failure.
2.2 Demographics¶
PAH is more prevalent in women (3.1x more than men), though men have higher mortality. CTEPH is more common in older adults with a history of thromboembolism.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
PH arises from complex interactions of genetic, epigenetic, and environmental factors. Key mechanisms include endothelial dysfunction, oxidative stress, and dysregulated signaling pathways (e.g., TGF- β /BMPR2 imbalance).
Table 294-2: FDA-Approved Therapies for PAH¶
| GENERIC NAME | ROUTE OF ADMINISTRATION | DRUG CLASS | INDICATION |
|---|---|---|---|
| Epoprostenol | IV | Prostacyclin derivative | Treatment of PAH to improve exercise capacity |
| Iloprost | Inhaled | Prostacyclin derivative | Treatment of PAH to improve composite endpoint |
| Treprostinil | IV or SC | Prostacyclin derivative | Treatment of PAH to diminish symptoms |
| Selexipag | Oral | Selective IP receptor agonist | Treatment of PAH to improve clinical outcomes |
| Bosentan | Oral | Endothelin receptor antagonist | Treatment of PAH to improve exercise capacity |
| Ambrisentan | Oral | Endothelin receptor antagonist | Treatment of PAH to delay clinical worsening |
| Sildenafil | Oral or IV | PDE5 inhibitor | Treatment of PAH to improve exercise ability |
| Riociguat | Oral | Soluble guanylyl cyclase stimulator | Treatment of PAH to improve exercise ability |
3.1 Genetic Drivers¶
BMPR2 mutations are the most common cause of hereditary PAH. Other genes (e.g., TBX4, SOX17) and epigenetic modifiers (e.g., TET2, DNMT3B) contribute to disease susceptibility.
3.2 Molecular Pathways¶
Dysregulation of BMPR2 signaling leads to increased activin ligand production, promoting vascular remodeling. Epigenetic changes (e.g., DNA methylation) and metabolic alterations (e.g., Warburg effect) further drive pathogenesis.
4. CLINICAL FEATURES¶
Symptoms include dyspnea, fatigue, and syncope. Physical findings may include right ventricular hypertrophy, elevated jugular venous pressure, and peripheral edema. Advanced stages present with right heart failure and systemic complications (e.g., hepatic congestion, renal failure).
4.1 Early vs. Advanced Stages¶
Early PH may be asymptomatic. Advanced stages show severe dyspnea, syncope, and signs of right heart failure (e.g., elevated JVP, hepatomegaly).
4.2 Systemic Manifestations¶
Right heart failure can lead to hepatic congestion, renal failure, and systemic hypertension. Myocardial atrophy and reduced capillary density are also observed.
5. DIFFERENTIAL DIAGNOSIS¶
PH must be differentiated from left heart failure, chronic obstructive pulmonary disease (COPD), and other causes of elevated pulmonary pressures. Key differentiators include the presence of right ventricular hypertrophy, elevated PVR, and specific imaging findings.
5.1 Left Heart Disease¶
Post-capillary PH is associated with left ventricular dysfunction, elevated left atrial pressure, and normal pulmonary artery wedge pressure (PAWP).
5.2 Chronic Thromboembolic Disease¶
CTEPH presents with obstructive pulmonary artery patterns on imaging and may lack typical features of PAH.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis requires right heart catheterization (RHC) to confirm mPAP >20 mmHg and PVR >2.0 WU. Echocardiography, chest imaging, and blood tests (e.g., BNP, NT-proBNP) support evaluation.
Table 294-1: World Symposium Classification¶
| GROUP | DESCRIPTION |
|---|---|
| GROUP 1 | Pulmonary arterial hypertension (PAH) |
| GROUP 2 | PH associated with left heart disease |
| GROUP 3 | PH associated with lung diseases/hypoxia |
| GROUP 4 | PH associated with pulmonary artery obstructions |
| GROUP 5 | PH with unclear/multifactorial mechanisms |
6.1 Diagnostic Algorithms¶
Echocardiography is the first-line test. If PH is suspected, RHC is required for definitive classification. CT pulmonary angiography is used for CTEPH screening.
6.2 Laboratory Tests¶
BNP/NT-proBNP correlate with right ventricular dysfunction. Serologic tests for autoimmune diseases (e.g., ANA, RF) and HIV are critical for differential diagnosis.
7. MANAGEMENT & TREATMENT¶
Treatment is tailored to PH subtypes. Pharmacologic options include endothelin receptor antagonists, PDE5 inhibitors, and prostacyclin analogs. Surgical interventions (e.g., pulmonary endarterectomy) are critical for CTEPH.
Table 294-2: FDA-Approved Therapies¶
| GENERIC NAME | ROUTE OF ADMINISTRATION | DRUG CLASS | INDICATION |
|---|---|---|---|
| Epoprostenol | IV | Prostacyclin derivative | Treatment of PAH to improve exercise capacity |
| Iloprost | Inhaled | Prost, derivative | Treatment of PAH to improve composite endpoint |
| Treprostinil | IV or SC | Prostacyclin derivative | Treatment of PAH to diminish symptoms |
| Selexip, Oral | Selective IP receptor agonist | Treatment of PAH to improve clinical outcomes | |
| Bosentan | Oral | Endothelin receptor antagonist | Treatment of PAH to improve exercise capacity |
| Ambrisentan | Oral | Endothelin receptor antagonist | Treatment of PAH to delay clinical worsening |
| Sildenafil | Oral or IV | PDE5 inhibitor | Treatment of PAH to improve exercise ability |
| Riociguat | Oral | Soluble guanylyl cyclase stimulator | Treatment of PAH to improve exercise ability |
7.1 Pharmacologic Therapies¶
Prostanoids (e.g., epoprostenol), PDE5 inhibitors (e.g., sildenafil), and ERAs (e.g., bosentan) are first-line. Riociguat (sGC stimulator) is used for refractory cases.
7.2 Surgical Options¶
Pulmonary endarterectomy is the gold standard for CTEPH. Balloon pulmonary angioplasty (BPA) is used for inoperable cases. Lung transplantation is reserved for advanced stages.
8. PROGNOSIS & COMPLICATIONS¶
Untreated PH leads to progressive right heart failure and high mortality. Prognosis varies by subtype, with PAH having a 5-year survival of ~30-50% and CTEPH having better outcomes with surgical intervention.
8.1 Survival Rates¶
PAH patients have 1-year survival of ~82% with optimal therapy, but this drops to ~58% at 5 years. CTEPH survival improves with endarterectomy (80-90%).
8.2 Complications¶
Complications include right heart failure, hepatic congestion, renal failure, and systemic hypertension. Myocardial atrophy and reduced capillary density are also observed.
9. SPECIAL CONSIDERATIONS¶
Special populations include pregnant women, children, and elderly patients. Pregnancy carries high risks, requiring multidisciplinary management. Elderly patients may have comorbidities (e.g., renal failure) affecting treatment choices.
9.1 Pregnancy¶
PAH in pregnancy is associated with high maternal mortality. Women with PAH should avoid pregnancy unless risks are carefully managed.
9.2 Elderly Patients¶
Elderly patients may have comorbidities (e.g., renal failure) requiring cautious use of vasodilators. Surgical options may be limited due to frailty.
10. KEY POINTS & CLINICAL PEARLS¶
- Early diagnosis and multidisciplinary management are critical for improving outcomes in PH.
- Genetic testing is essential for hereditary PAH, particularly in families with BMPR2 mutations.
- Right heart catheterization is the gold standard for diagnosing PH and classifying subtypes.
- Combination therapy (e.g., ERAs + PDE5 inhibitors) is recommended for most PAH patients.
- CTEPH is curable with pulmonary endarterectomy or BPA in selected cases.