Definition

 • A mean pulmonary artery pressure >25 mmHg at rest or >30 mmHg during exercise.

Subtypes

 • Secondary pulmonary hypertension is a complication of chronic lung or cardiac disease.

• Primary pulmonary hypertension occurs in the absence of chronic lung or heart disease.

Epidemiology

 • Secondary pulmonary hypertension is quite common.

• Primary pulmonary hypertension is rare.

Aetiology

• Common causes of secondary hypertension include COPD, interstitial lung disease, left ventricular failure (LVF), and chronic pulmonary thromboemboli.

 • Primary pulmonary hypertension may be idiopathic or associated with certain drugs, HIV infection, collagen vascular disease, and congenital systemic-to-pulmonary shunts.

Pathogenesis

 • Chronic hypoxia and obliterative pulmonary fibrosis both lead to the development of raised pressure in the pulmonary arterial circulation.

Presentation

 • Secondary pulmonary hypertension causes worsening of the symptoms of the pre- existing condition with increasing breathlessness.

• Primary pulmonary hypertension presents with exertional dyspnoea and fatigue. Dizziness and syncope are also common.

Macroscopy

 • the presence of atherosclerosis in large pulmonary arteries is a clue to underlying pulmonary hypertension.

 • Right ventricular hypertrophy may also be present.

Histopathology

 • Muscular hypertrophy and intimal proliferation of small pulmonary arteries and muscularization of pulmonary arterioles.

 • Severe cases show plexiform lesions, characterized by a proliferation of slit- like vascular spaces from the arterial wall.

 • Very severe cases may display fibrinoid necrosis of the arterial wall.

 Prognosis

• Secondary pulmonary hypertension generally implies significant underlying cardiac or lung disease with poor prognosis.

 • Prognosis of primary pulmonary hypertension is also very poor with 5- year survival rates of only 25– 50%.