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 right heart ventricle heart to pump blood forward, eventually leading to causing the right-sided heart muscle to weakening and progressive right heart failure.
When pulmonary hypertension 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 pulmonary arterial hypertension 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 certain diet weight loss drugs like fenfluramine and dexfenfluramine.
There are also other causes of secondary pulmonary hypertension, that are not known as pulmonary arterial hypertension. Pulmonary hypertension can be divided into 5 different groups, according to the World Health Organisation (WHO) classification. Pulmonary arterial hypertension classified as WHO Group 1 pulmonary hypertension. There are also WHO Group 2, 3, 4, 5 pulmonary hypertension, that are related to different underlying causes and are treated differently. WHO Group 2 pulmonary hypertension is related to left heart disease (e.g. left sided valve disorder and left sided heart pump failure). WHO group 3 pulmonary hypertension is related to e include lung disorders (emphysema, lung fibrosis, sleep apnea). WHO Group 4 pulmonary hypertension is due to, chronic pulmonary thromboembolism (chronic formation of blood clots in the pulmonary artery). WHO Group 5 pulmonary hypertension is related to haemotological and malignant disorders or endocrine conditions. These different groups of pulmonary hypertension must be clarified by a series of comprehensive investigations before determining diagnosis, risk, prognosis and treatment.
These test 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
- Six minute walk test - assess the ability of the patient to perform physical activities
- Lung scans (CT and VQ scans) - to look for lung problems and for clots in the lung vessels
- Blood tests such as for SLE, liver disease, AIDS and others that can cause pulmonary hypertension
- Lung Function Studies - assess the function of the lungs
- Sleep studies - to exclude obstructive sleep apnea as a cause
- Right heart catheterisation - a definitive test to prove the diagnosis, to exclude shunts and left heart disease and to prognosticate the condition
As the symptoms of this disease are rather common, it is usually mistaken for asthma.
Common symptoms of pulmonary hypertension include:
- Breathlessness, especially on exertion
- Tiredness - dizziness during physical exertion
- Swollen ankle and legs
- Fainting
- Chest pain during physical activity
Pulmonary hypertension is a serious diagnosis and must be investigated thoroughly. As pulmonary arterial hypertension is progressive and lead to rapid deterioration with right-sided heart failure, diagnosis and treatment should be done early for improved outcomes. Outcomes of the treatment is dependent on the cause of the disease as well. 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 pulmonary hypertension in Singapore include:
- Phosphodiesterase V inhibitors such as Sildenafil, Tadalafil
- Endothelin Receptor Antagonists such as Bosentan, Macitentan, Ambrisentan
- Prostaclyclin analogues such as inhaled Iloprost, intravenous Veletri, subcutaneous or inhaled Treprostinil
- Guanylyl Cyclase stimulators such as Riociguat
- Activin inhibitors such as Sotatercept
A patient can sometimes require treatment using two or three types of these drugs in combination as their disease progresses.
Drugs that are commonly used to complement the treatment of pulmonary hypertension include:
- Anticoagulants – Warfarin, Apixaban, Rivoroxivaban - these are blood thinning medication that prevents clot formation in lung arteries
- Diuretics - Spironolactone, Frusemide (with Potassium Chloride) - these medications help to remove water logged in the body
- Long term Oxygen therapy - This is offered to patients with low oxygen saturation (< 90%), as oxygen is a good dilator of the pulmonary blood vessels.
Specific to patients with WHO Group 4 thromboembolic pulmonary hypertension, patients will be assessed for other specific treatments such as pulmonary endarterectomy (open heart surgery) or balloon pulmonary angioplasty (catheter directed balloon dilation of distal pulmonary arteries).
