Pulmonary Hypertension

Pulmonary Arterial Hypertension (PAH) is a rare blood vessel disorder of the lung in which the pressure in the pulmonary artery (the blood vessel that leads from the heart to the lungs) rises above normal levels and may become life threatening.

In the advanced stage of the disease, the blood vessels in the lungs are narrowed, thickened and stiff, causing difficulty for the heart to pump blood through, causing the heart muscle to weaken over time. Clots can form and block part of the vessel's lumen as well.

When PAH occurs in the absence of a known cause, it is referred to as Idiopathic Pulmonary Arterial Hypertension (IPAH). IPAH is extremely rare, occurring in about 2 to 10 persons per a million population per year. Causes of PAH include collagen vascular diseases (e.g. scleroderma, CREST syndrome or systemic lupus erythematosus), congenital heart diseases (shunts like ventricular and atrial septal defects), HIV infection, liver disease and diet drugs like fenfluramine and dexfenfluramine.

Common causes of secondary PAH include lung disorders (emphysema, lung fibrosis, sleep apnea), chronic pulmonary thromboembolism (chronic formation of blood clots in the pulmonary artery), and left heart disease (e.g. mitral stenosis).

As the symptoms of this disease are rather common, PAH is usually mistaken for asthma.

Common symptoms of PAH include:

• Breathlessness, especially on exertion
• Tiredness - dizziness during physical exertion
• Swollen ankle and legs
• Fainting
• Chest pain during physical activity

These tests are necessary in order for the doctor to assess your pulmonary arterial pressure and to determine the cause if the pressures are high.

• Echocardiography can estimate the pressure in the lung vessels and exclude cardiac conditions as a cause
• The six- minute walk test assesses the ability of the patient to perform physical activities
• Lung scans (CT and VQ scans) are used to look for lung problems and for clots in the lung vessels
• Blood tests, such as for SLE, liver disease, AIDS and other conditions that can cause PAH
• Lung Function Studies assess the function of the lungs
• Sleep studies are used to to exclude obstructive sleep apnea as a cause
• Right heart catheterisation is a definitive test to prove the diagnosis, to exclude shunts and left heart disease, and to prognosticate the condition

PAH has a poor prognosis and must be investigated. Patients who have symptoms need to be treated early. Outcomes of the treatment is largely dependent on the cause of the disease. Treatment with PAH specific therapy has been shown to improve symptoms, exercise capacity and overall prognosis of the disease.

Drugs that are used specifically for treatment of PAH in Singapore include:

• Phosphodiesterase V inhibitors such as Sildenafil (Viagra), Tadalafil (Cialis)
• Endothelin Receptor Antagonists such as Bosentan (Tracleer)
• Prostaclyclin analogues such as Inhaled Iloprost (Ventavis), Intravenous Epoprostenol (Flolan), thermostable epoprostenol, Veletri
• Guanylyl Cyclase stimulators such as Riociguat

A patient can sometimes require treatment using two or three types of these drugs in combination as the disease progresses.

Drugs that are commonly used to complement the treatment of PAH include:

• Warfarin, which is an anticoagulant that thins the blood.
• Diuretics like Spironolactone, Frusemide (with Potassium Chloride). These medications helps to remove water logged in the body.
• Long term oxygen therapy, which is offered to patients with low oxygen saturation (< 90%), as oxygen is a good dilator of the pulmonary blood vessels.

Patients with Thromboembolic Pulmonary Hypertension can be assessed with modalities like dual energy CT angiography or rotational angiography. Patients will be assessed for suitability for pulmonary endarterectomy.

Patients with distal embolic disease can be treated with balloon pulmonary angioplasty (BPA).