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Idiopathic pulmonary arterial hypertension (IPAH) is a type of pulmonary arterial hypertension (PAH) without any known cause. However, symptoms, diagnosis, and treatments for the condition are similar to those of other forms of pulmonary arterial hypertension.
There are several types of pulmonary hypertension (PH) — high blood pressure specifically in the vessels between the heart and lungs. The World Health Organization (WHO) categorizes the different types of PH into five groups. Group 1 comprises a type called pulmonary arterial hypertension, characterized by blood vessels in the lungs becoming narrowed, blocked, or destroyed.
Idiopathic pulmonary arterial hypertension is a subtype of PAH. “Idiopathic” means the cause isn’t known.
In PAH, narrow, blocked, or damaged vessels in the lungs hinder blood flow, which increases the blood pressure within the vessels. When a person has PH, their pulmonary arterial pressure is 25 millimeters of mercury (mmHG) or more at rest. (A normal pulmonary arterial pressure is 8-20 mmHg at rest.) The right side of the heart is responsible for pumping blood to the lungs to pick up oxygen through a large blood vessel called the pulmonary artery. When the lung’s blood vessels are narrowed or blocked, the right side of the heart has to work harder to pump blood to the lungs. Over time, the overworked heart muscle weakens.
High blood pressure in the lung arteries can lead to the damage of a valve in the heart that separates the two right-side chambers. The damaged valve does not close properly as the heart pumps, and it can let blood flow backward in the heart (tricuspid valve regurgitation). PAH can eventually lead to right-sided heart failure, or failure of the right side of the heart
IPAH is a rare disease. The prevalence of IPAH is estimated to be as low as 5.9 cases per one million adults. Every year, there are about 2.4 new cases of PAH diagnosed per one million adults.
The cause of IPAH is unknown. One theory is, IPAH could be caused by injury to the cells in the blood vessels of the heart, potentially leading to vascular disease (disease of the blood vessels). Lesions (growths) are common in the lung blood vessels of people with PAH, which can contribute to the vessels becoming too narrow.
Other types of PAH typically have known causes. For example, heritable PAH is caused by inherited genetic mutations, often in a gene called BMPR2, which controls the growth of cells in blood vessels. Other kinds of PAH can be caused by:
IPAH can have genetic mutations, but unlike heritable PAH, there is no family history of the disease.
Although the early stages of IPAH may not have any symptoms, progressive damage to the heart and lungs can cause more severe symptoms of PAH. The symptoms of all PAH types are also common to other lung diseases such as chronic obstructive pulmonary disease, asthma, and emphysema. These symptoms include:
Shortness of breath is the most common symptom of PAH. Fainting (syncope) can also occur.
Diagnosing PAH can be difficult because the symptoms are very similar to those of other lung diseases. IPAH can be particularly tricky to diagnose as it has no discernible cause. Your doctor may run several tests to help determine if you have PAH if you show symptoms. Most of these tests can be used to rule out other causes, which can help your doctor narrow in on PAH.
Blood tests measure several aspects of your health, such as oxygen level, liver and kidney function, and any present infection. Measurement of a protein called brain natriuretic peptide in the blood can be used to determine how much strain the heart is experiencing..
Chest X-rays are used to take images of the heart and lungs. This can help your doctor find any scarring in your lungs (interstitial fibrosis) or an enlarged ride side (right ventricle) of the heart.
Echocardiography is a noninvasive way to take pictures of the heart, similar to an ultrasound. An echocardiogram image can help a doctor estimate heart function and pressure in the heart, with higher pressure indicating hypertension.
The doctor may also perform a pair of nuclear scans, a pulmonary ventilation scan and a perfusion scan (collectively called a VQ scan). This method creates an image of the air and blood flow in the lungs using a small amount of radioactive material. It’s useful for finding any blood clots in the lungs.
An electrocardiogram (EKG) is a noninvasive method for measuring the electrical signals of the heart. An EKG can be helpful in determining if the heart is working properly.
Pulmonary function tests (or lung function tests) measure how well the lungs are working. One of the most common tests is spirometry, which involves blowing into a tube attached to a machine that measures your lung capacity.
An exercise-tolerance test determines your ability to exercise, which is related to your ability to properly pump oxygen throughout the body. A common test is the six-minute walk test, in which the doctor has you walk for six minutes to see how your breathing or symptoms are affected.
Right heart catheterization is a gold-standard test for PH diagnosis — and is also more invasive than some other tests. In this test, a doctor runs a small tube (catheter) through a large vein in the arm, neck, or groin and into the heart and lung blood vessels to measure blood pressure.
For people already diagnosed with pulmonary hypertension, a vasodilator study can help determine how much the lung blood vessels relax and open up over time. Information from this test can help your doctor choose a treatment or estimate a prognosis.
There is no cure yet for any type of PAH, but several treatments exist that can help improve heart and lung function. Treatment of pulmonary hypertension is designed to relieve symptoms and slow disease progression.
Different medications can be taken by mouth (orally), inhalation, or intravenously. In severe cases of PAH, a combination of therapies can be beneficial.
Phosphodiesterase-5 (PDE5) inhibitors allow the lungs to relax so that the blood vessels open up more (vasodilate). Dilation allows blood to flow more easily through the vessels, which lowers blood pressure and reduces strain on the heart.
One example of a PDE5 inhibitor is the drug Revatio (sildenafil).
Endothelin receptor antagonists (ERAs) prevent blood vessels from narrowing. They may help people with PH perform physical activities without too much strain. Endothelin is a compound made naturally in the body that causes blood vessels to restrict and narrow. Endothelin can also cause abnormal growth of the muscle in lung blood vessels, which further restricts blood flow. Blocking endothelin with ERAs helps lung blood vessels to relax and open up, allowing better blood flow and reducing strain on the heart.
Some ERAs include Letairis (ambrisentan) and Tracleer (bosentan).
Prostacyclin is a compound naturally produced in the body that makes blood vessels widen. A class of medications called prostanoids act like prostacyclin to widen the narrowed blood vessels that drive high blood pressure in IPAH. Some of these medications include:
Epoprostenol can be taken long-term through a surgically implanted central venous catheter with a pump, which continuously flows medication into the body. Epoprostenol for short-term use is typically administered through a small IV in the arm.
In the body, prostacyclin has to bind to a specific receptor to signal the blood vessels to widen. A class of drugs called prostacyclin receptor agonists can mimic prostacyclin and bind to the prostacyclin IP receptor. Binding of the receptor leads to widening of the blood vessels. One prostacyclin receptor agonist is called Uptravi (selexipag).
Cyclic GMP (cGMP) is a compound naturally made in the body that makes blood vessels relax and widen. It’s made by an enzyme called guanylate cyclase. Some medications can stimulate the enzyme so that it makes more cGMP, leading to the widening of blood vessels. These drugs, such as Adempas (riociguat), help vessels of the lungs dilate. This, in turn, can improve your ability to exercise and help prevent signs and symptoms from worsening.
Calcium channel blockers help blood vessels throughout the body open up. A doctor can determine how well someone with PAH responds to this type of drug during a right heart catheterization. The Pulmonary Hypertension Association notes that calcium channel blockers only benefit people with IPAH and not other types of PH.
Severe cases of IPAH may require a heart-lung, single lung, or double lung transplant. Transplantation is a last-resort surgical procedure in which the diseased heart or lungs are replaced by healthy organs from a donor. A transplant surgery is only recommended for a small number of people with PH, as medications can often relieve the symptoms and progression of the disease.
Supportive therapy treatments can be used for IPAH.
Daily exercise is one way to strengthen your heart so that it can pump blood more effectively. Pulmonary rehabilitation is an exercise program specifically to help those with lung disease perform exercises that are not too difficult. A review of several studies on exercise in people with PAH found that exercise tailored to people with PAH improved blood flow and quality of life.
The American Lung Association recommends avoiding hot tubs, saunas, and high altitudes to limit strain on the heart and lungs. A healthy diet that limits salt, cholesterol, and saturated fat can also reduce the strain on the heart in PAH.
Living with pulmonary hypertension has its challenges. It can help to know that you’re not alone. By joining myPHteam, the social network for people with PH and their loved ones, you can connect with a growing team of more than 35,000 members from across the globe who understand life with pulmonary hypertension.
Are you living with IPAH? Share your thoughts in the comments below or by posting on myPHteam.
Allen J. Blaivas, D.O.
is certified by the American Board of Internal Medicine in Critical Care Medicine, Pulmonary Disease, and Sleep Medicine. Review provided by VeriMed Healthcare Network.
Learn more about him here.
Ashley Knox
is a doctoral candidate at the University of Colorado, where she studies the noncoding RNAs involved in gammaherpesvirus pathogenesis.
Learn more about her here.
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