What are examples of Group 4 pulmonary hypertension?

Group 4 Pulmonary Hypertension: Clinical Examples

Group 4 pulmonary hypertension is formally named "Chronic Thromboembolic Pulmonary Hypertension (CTEPH) and Other Pulmonary Artery Obstructions" and includes six distinct clinical entities beyond CTEPH itself. 1

Primary Condition: Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

• CTEPH is the predominant condition in Group 4, characterized by persistent organized thromboembolic material obstructing pulmonary arteries after incomplete resolution of acute pulmonary embolism. 2, 3

• CTEPH occurs in approximately 3% of acute pulmonary embolism survivors, though a prior documented venous thromboembolic episode is not always present. 2, 4

• The pathophysiology involves mechanical obstruction of proximal (lobar-to-segmental) and distal (subsegmental) pulmonary arteries, with secondary arteriopathic changes in non-occluded vessels. 2, 4

Other Pulmonary Artery Obstructions in Group 4

The European Society of Cardiology/European Respiratory Society guidelines specifically list five additional causes of pulmonary artery obstruction that comprise Group 4: 1

Malignant Obstructions

• Pulmonary angiosarcoma: A rare intravascular tumor causing mechanical obstruction of pulmonary arteries. 1

• Other intravascular tumors: Various neoplastic processes that grow within or invade pulmonary vessels. 1

Inflammatory and Infectious Causes

• Arteritis: Inflammatory conditions affecting the pulmonary arterial walls leading to stenosis or obstruction. 1

• Parasitic disease (hydatidosis): Echinococcal cysts causing mechanical obstruction of pulmonary vessels. 1

Congenital Abnormalities

• Congenital pulmonary artery stenoses: Developmental narrowing of pulmonary arteries present from birth. 1

Hemodynamic Characteristics

• Group 4 pulmonary hypertension demonstrates pre-capillary hemodynamics with mean pulmonary arterial pressure ≥25 mmHg, pulmonary arterial wedge pressure ≤15 mmHg, and pulmonary vascular resistance >3 Wood units. 1

• These hemodynamic features distinguish Group 4 from post-capillary pulmonary hypertension due to left heart disease (Group 2). 1

Diagnostic Approach

• Ventilation/perfusion (V/Q) lung scanning is the recommended screening test to distinguish Group 4 from other forms of pulmonary hypertension, showing multiple segmental perfusion defects in CTEPH. 1

• CT pulmonary angiography, right heart catheterization, and selective pulmonary angiography are required for definitive diagnosis and assessment of treatment suitability. 1, 2

• A critical pitfall: CT pulmonary angiography alone may miss the diagnosis of CTEPH, making V/Q scanning essential in the diagnostic algorithm. 1

Clinical Significance

• CTEPH is potentially curable with pulmonary thromboendarterectomy surgery, distinguishing it from most other forms of pulmonary hypertension. 2, 3

• More than one-third of patients may be inoperable, requiring alternative treatments including balloon pulmonary angioplasty or medical therapy. 2, 3