Pulmonary hypertension

Pulmonary hypertension

Definition

A pulmonary arterial pressure greater than 30/20 mmHg.

Aetiology

Pulmonary hypertension may be secondary to a variety of diseases, or more rarely a primary idiopathic form. Causes can be divided into

1.      Increased blood volume passing through the pulmonary circulation as occurs in left to right shunting (septal defects, persistent ductus arteriosus).

2.     Increased left atrial pressure, which causes an increase in pulmonary venous pressure. This in turn raises the pulmonary capillary and arterial pressures (left ventricular failure, mitral valve disease, cardiomyopathy).

3.     Increased pulmonary vascular resistance:

·        Chronic lung disease such as chronic bronchitis, emphysema and pulmonary fibrosis partly due to the vasoconstriction associated with hypoxia.

·        Chronic pulmonary thromboembolic disease due

to occlusion of part of the vasculature and hypoxia. Primary pulmonary hypertension is seen predominantly in young females. A similar syndrome is associated with sytemic lupus erythematosus, scleroderma and Raynaud’s disease.

Pathophysiology

Increased pulmonary arterial pressure causes irreversible structural changes in the pulmonary vasculature due to increasing amounts of smooth muscle. The result is a decrease in the lumen of the vessels and hence an increased afterload on the right side of the heart. Progressive failure of the right side of the heart occurs which is called ‘cor pulmonale’.

Clinical features

Dyspnoea, syncope and fatigue are common. Symptoms of the underlying cause and of right ventricular failure may also be present.

Signs are a result of the elevated pressures within the pulmonary circulation. There is elevation of the JVP with a prominent ‘a’ wave, a forceful parasternal heave due to increased right ventricular stroke work, and a loud pulmonary component to the second heart sound. Right heart failure leads to peripheral oedema and hepatomegaly.

A pulmonary mid systolic ejection murmur and an early diastolic murmur of pulmonary regurgitation may be heard (Graham–Steel murmur).

If tricuspid regurgitation develops there will be a pansystolic murmur and a large ‘v’ wave in the JVP.

Microscopy

If pulmonary hypertension is long-standing, microscopy reveals hypertrophy of the media of the vessels with an increase in the amount of smooth muscle. There is worsening occlusion of the lumen of the vessels.

Investigations

A chest X-ray may show right ventricular and right atrial enlargement. The central pulmonary arteries are usually prominent and may be ‘pruned’ peripherally.

The ECG shows right ventricular hypertrophy with right axis deviation: Prominent R wave in V1, and inverted T waves in the V1–V3. The right atrial enlargement results in tall peaked P waves.

Underlying causes should be identified wherever possible.

Management

Treatment is aimed at the underlying cause.

Congenital abnormalities such as septal defects should be corrected wherever possible, mitral valve disease may indicate surgical intervention and left ventricular failure should be treated.

Pulmonary hypertension secondary to chronic lung disease may benefit from oxygen therapy to reduce the vasoconstrictor effect of hypoxia.

Long-term intravenous infusion of epoprostenol (prostacyclin) improves the outcome of patients with primary pulmonary hypertension. The administration of bosentan (a nonselective endothelin receptor antagonist) may also be beneficial in patients with primary pulmonary hypertension although longterm followup data are not yet available.

When there are irreversible vascular changes the condition is progressive. Heart–lung transplantation is recommended in younger patients.