Systemic sclerosis-associated pulmonary arterial hypertension

Systemic sclerosis-associated pulmonary arterial hypertension (SSC-PAH) occurs when fibrosis causes the walls of the pulmonary arteries to thicken. This raises the blood pressure within these critical vessels, placing additional strain upon the heart. The onset of SSc-PAH can be very slow, and symptoms may be so mild at first that you may not realise that something has changed. If you or your family have noticed that you are getting breathless, even if this seems mild, it is important to tell your doctor.

Pulmonary hypertension (PH) means high blood pressure within the pulmonary arteries: the main vessels carrying blood to the lungs from the heart. This can damage the right side of the heart, so that it cannot work properly. When the cause is narrowing of the small blood vessels this is called pulmonary arterial hypertension (PAH). It is thought that around one-in-ten people with scleroderma could develop SSc-PAH, although this may not occur until many years after the onset of systemic sclerosis.

What is SSc-PAH?

In SSc-PAH, inflammation and scarring within the blood vessels of the lungs may thicken the walls of the pulmonary artery, so that it no longer opens up easily to relieve the pressure of the blood inside. This may lead to a significant build-up of pressure in the vessels feeding into the lungs from the heart, so that blood pressure in the pulmonary artery is higher than normal. This affects the small blood vessels of the lungs, so that there is less blood reaching the lungs and less oxygen carried within the bloodstream. The high pressure then leads to a stretching of the right side of the heart, meaning that it has to work harder. 

Symptoms

Symptoms are caused by either reduced oxygen levels in the bloodstream or by the additional strain placed upon the heart.   

• Shortness of breath with minimal exertion
• Tiredness
• Fatigue
• Dizzy spells or blackouts
• Chest pain 
• Swelling in the ankles or legs

Diagnosis

Because there are effective treatments available for SSc-PAH, early detection is vital. Initial investigations may include all of the following:

• Ultrasound of the heart (echocardiogram)
• Breathing tests (pulmonary function tests)
• Exercise tests
• X-rays (including CT and MRI)

In many cases, the earlier these changes are diagnosed the better the outlook, because you can then be carefully monitored and offered treatment where necessary. Routine, annual testing to assess your lung and heart function, as well as your blood pressure and kidney function, are therefore critical for detecting any problems, including the onset of SSc-PAH. You are entitled to have these tests regularly, so do not be afraid to ask your doctor if they are not being carried out.

Treatment

There are a number of effective treatments available, although the best option will depend on several factors, including the nature and severity of symptoms.

There are certain options that may be prescribed to help maintain wellbeing and help you continue living as actively as possible:

• Oxygen therapy: In some cases, continuous oxygen therapy may be suitable for people with very low oxygen levels in the blood. It helps to stabilise the level of oxygen, helping you to breathe more easily. If you are travelling, you may need to have oxygen with you for your flight and also in transit.

• Anticoagulants: some forms of PAH carry an increased risk of developing blood clots. Anticoagulant medicines including warfarin can help to prevent this and enable blood to flow more freely.

• Diuretics or water tablets: these work by increasing urine output and are used to remove excess fluid from the body to reduce the strain upon the heart. Removing water from the blood decreases the amount of fluid within the blood vessels, which also reduces pressure. Diuretics also treat symptoms like swollen ankles.

Other therapies are more targeted treatments, that will aim to slow down the progression of your condition and may even reverse some of the damage to the heart and lungs. These include:

• Calcium channel blockers: these are vasodilators that are used to help open up the blood vessels. This group of medications includes nifedipine, diltiazem, nicardipine and amlodipine.

• Endothelin receptor antagonists (ERAs): these are a form of targeted therapy used to slow the progression of PAH by reducing the level of endothelin within the blood. These medications include bosentan, ambrisentan and macitetan.

• Phosphodiesterase 5 (PDE 5) inhibitors: are another targeted therapy that aims to slow progression and limit some of the impact. PDE 5 inhibitors include sildenafil and tadalafil and are widely used as a treatment for erectile dysfunction, because the blood vessels are so similar. They work by inhibiting an enzyme called phosphodiesterase type 5 [PDE5] from working, which helps blood vessels to relax, increasing blood flow and lowering blood pressure.

• Prostanoids: are powerful vasodilators that are used to enable blood to flow more freely through the vessels of the lungs, ultimately reducing the strain upon the heart. This group of medications work in a similar way to prostaglandins, that occur naturally within the body. In the longer term, the beneficial effect upon the heart may mean that it is able to work more efficiently. Examples of prostanoids include epoprostenol, iloprost and treprostinil.

• Soluble guanylate cyclase stimulators: these are a form of targeted therapy used to slow down disease progression. This is prescribed in the form of riociguat tablets, that work by causing the blood vessels in the lungs to dilate.

• Inhaled treatments: these include nebulised iloprost. This is a vasodilator used to open up the blood vessels of the lungs, allowing blood to flow more freely.

Living with SSc-PAH

A diagnosis of SSc-PAH is likely to affect your daily life to some degree. You may notice that you are becoming tired more easily, or feel breathless when walking short distances or climbing the stairs. Because the onset of this condition is often very slow, it is vital to tell your doctor if you notice any changes, because early detection is important and there are effective treatments available to help. There are also a number of specialist PH centres across the UK, where you may be referred for diagnosis and ongoing management if necessary. For more information, talk to your doctor or nurse specialist who will be able to help.

We would like to thank Dr Colin Church of the Scottish Pulmonary Vascular Unit in Glasgow for his help and support in producing this article.