How do you classify pulmonary hypertension?

Classification of Pulmonary Hypertension

Pulmonary hypertension is classified into five main groups based on etiology, pathophysiological mechanisms, and therapeutic approach, as outlined by the Dana Point classification (2008) and refined in the ESC/ERS guidelines. 1

Definition of Pulmonary Hypertension

Pulmonary hypertension (PH) is defined as:

• Mean pulmonary arterial pressure (PAP) ≥25 mmHg at rest as assessed by right heart catheterization 2, 1
• This hemodynamic and pathophysiological condition can be found in multiple clinical conditions 2

The Five Main Classification Groups

Group 1: Pulmonary Arterial Hypertension (PAH)

• Characterized by pre-capillary PH with normal pulmonary wedge pressure ≤15 mmHg 2, 1
• Includes:
  • 1.1 Idiopathic
  • 1.2 Heritable (BMPR2, ALK1, endoglin mutations)
  • 1.3 Drug and toxin-induced
  • 1.4 Associated PAH (APAH):
    • Connective tissue diseases
    • HIV infection
    • Portal hypertension
    • Congenital heart disease
    • Schistosomiasis
    • Chronic hemolytic anemia
  • 1.5 Persistent pulmonary hypertension of the newborn
  • 1' Pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis 2

Group 2: PH Due to Left Heart Disease

• Post-capillary PH with elevated pulmonary wedge pressure >15 mmHg 1
• Includes:
  • 2.1 Systolic dysfunction
  • 2.2 Diastolic dysfunction
  • 2.3 Valvular disease 2

Group 3: PH Due to Lung Diseases and/or Hypoxemia

• Includes:
  • 3.1 Chronic obstructive pulmonary disease
  • 3.2 Interstitial lung disease
  • 3.3 Other pulmonary diseases with mixed restrictive and obstructive pattern
  • 3.4 Sleep-disordered breathing
  • 3.5 Alveolar hypoventilation disorders
  • 3.6 Chronic exposure to high altitude
  • 3.7 Developmental abnormalities 2

Group 4: Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

• Caused by obstruction of pulmonary arteries by organized thrombi 2, 3
• Surgical pulmonary endarterectomy is the treatment of choice for eligible patients 3

Group 5: PH with Unclear and/or Multifactorial Mechanisms

• Includes:
  • 5.1 Hematological disorders (myeloproliferative disorders, splenectomy)
  • 5.2 Systemic disorders (sarcoidosis, pulmonary Langerhans cell histiocytosis)
  • 5.3 Metabolic disorders (glycogen storage disease, Gaucher disease, thyroid disorders)
  • 5.4 Others (tumoral obstruction, fibrosing mediastinitis, chronic renal failure on dialysis) 2

Hemodynamic Classification

Pulmonary hypertension is also classified hemodynamically:

1. Pre-capillary PH:

   • Mean PAP ≥25 mmHg
   • Pulmonary wedge pressure (PWP) ≤15 mmHg
   • Pulmonary vascular resistance >3 Wood units 1, 4

2. Post-capillary PH:

   • Mean PAP ≥25 mmHg
   • Pulmonary wedge pressure >15 mmHg 1

Clinical Significance of Classification

The classification system guides:

• Diagnostic approach
• Treatment decisions
• Prognosis assessment 1, 3

For example:

• Group 1 (PAH) patients may benefit from specific PAH therapies like endothelin receptor antagonists, phosphodiesterase-5 inhibitors, and prostacyclin analogs 5, 6, 4
• Group 4 (CTEPH) patients should be evaluated for pulmonary endarterectomy 3
• Treatment for Groups 2,3, and 5 primarily focuses on the underlying condition 7, 3

Important Considerations

• Right heart catheterization is essential for accurate diagnosis and classification 3
• Transthoracic echocardiography is used for initial screening and estimating the probability of PH 1, 3
• All patients with suspected PAH or CTEPH should be referred to specialized centers 3
• The classification system continues to evolve as understanding of PH pathophysiology improves 8

This classification system provides a structured approach to understanding the diverse conditions that can lead to pulmonary hypertension and guides appropriate treatment strategies based on the underlying pathophysiology.