This type of pulmonary hypertension is caused by chronic (long standing or old) blood clots in the arteries of the lung. It is often referred to in its shortened form of CTEPH.
Lots of people develop blood clots (also called pulmonary emboli or PEs) in the lung arteries but usually your body breaks down the clots within 3 months and you return to normal. Patients with PEs will probably be given warfarin or another anticoagulant to prevent any new clots forming. Unfortunately, in a small number of patients who have a PE (approximately 2–4%) the blood clots do not break down fully and the patient will develop CTEPH.
Some people are more likely to develop PE than others but in some cases, there is no clear reason why a person develops a PE, and no one really understands why a small number of people with PEs then go on to develop CTEPH.
Some known causes and risk factors for CTEPH include:
• Large or recurrent PEs
• A previous blood clot in a deep vein of the leg, also called deep vein thrombosis (DVT)
• Cancer or previous cancer
• Removal of the spleen (splenectomy)
• Chronic inflammatory diseases, such as inflammatory bowel disease
• Certain blood clotting disorders, such as antiphospholipid syndrome (a disorder of the immune system that causes an increased risk of blood clots).
Treatment for your CTEPH falls into one of four categories:
A diagnosis of CTEPH brings with it a need for life-long anticoagulation medication, unless there is a medical reason for not taking it. Anticoagulants are used to prevent further clots forming rather than breaking down the chronic clots that are already present.
The most commonly used anticoagulant is warfarin. Patients on warfarin are monitored by a regular blood test called the INR (international normalised ratio), which monitors how quickly your blood clots. For most patients in the UK prescribed warfarin, the target INR is 2.5, with a range of 2.0–3.0.
Other patients are treated with injections of low molecular weight heparin, e.g. enoxaparin (Clexane®) or dalteparin (Fragmin®) or a synthetic anticoagulant called Fondaparinux. These are most commonly used if your INR is less than 2 or if you have had recurrent PEs despite treatment with warfarin. There are an increasing number of alternative oral anticoagulants to warfarin, such as apixaban, dabigatran and rivaroxaban, that do not need to be monitored but their effectiveness has not been assessed in patients with CTEPH.
PEA is an operation to remove the scars made by old blood clots in the pulmonary arteries. Approximately 60-70% of patients with CTEPH are suitable for PEA. It is complex surgery and Papworth Hospital is the only centre in the UK that performs this operation. PEA is the treatment of choice for patients with CTEPH because it is potentially curative. It can also significantly improve patient symptoms, quality of life and gives the best chance of long-term survival. However, there are risks as well as benefits with PEA and some patients may not benefit fully due to residual PH after the surgery.
The pioneering procedure is now a treatment option for patients with Chronic Thromboembolic Pulmonary Hypertension (CTEPH) who are unsuitable for surgery.
The procedure sees an interventionist cardiologist insert a very fine wire into blood vessels in the lungs and guide a tiny balloon into position. The balloon is inflated, to around the size of a pea, for a few seconds to push the blockage aside and restore blood flow to the lung tissue. The balloon is then deflated and removed. This can be repeated several times in different parts of the lung during a single treatment session.
BPA usually involves up to four treatment sessions in the hospital’s Catheter Labs, each lasting up to two hours, spaced four to six weeks apart.
The procedure is performed under a light sedation and local anaesthetic; this means that you are given a combination of medicines to help you relax and to block the pain. You may feel very sleepy but will be able to respond to instructions.
Tablets are used for the treatment of patients with CTEPH in two main scenarios:
• To improve symptoms while waiting for PEA. This will usually be sildenafil and is an unlicensed treatment. The drug is well tolerated and is usually stopped immediately after your surgery.
• In patients where the distribution of the scars are not suitable for PEA or who have residual PH following surgery. This will usually be riociguat (Adempas®) and is the only licensed therapy for patients with CTEPH. This has been shown to improve exercise capacity and breathlessness in patients with CTEPH. Riociguat is taken 3 times a day and the dose is slowly increased over 8 weeks until the optimum treatment dose is reached.
Both of these tablets have been shown to interact with medicines called nitrates which are used to treat ischaemic heart disease (also known as coronary heart disease) such as angina (chest pain), heart attacks and heart failure, so they cannot be used by patients who are taking these medicines.
If you are taking nitrates and your CTEPH is not suitable for surgery, your specialist PH centre may consider other treatment options including endothelin receptor antagonists or prostanoid medication. Your specialist physician will discuss these options with you.