Question: what are the causes of pulmonary hypertension

Reference:
 Pulmonary hypertension Overview Pulmonary hypertension is a type of high blood pressure that affects the arteries in your lungs and the right side of your heart. In one form of pulmonary hypertension, tiny arteries in your lungs, called pulmonary arterioles, and capillaries become narrowed, blocked or destroyed. This makes it harder for blood to flow through your lungs, and raises pressure within your lungs' arteries. As the pressure builds, your heart's lower right chamber (right ventricle) must work harder to pump blood through your lungs, eventually causing your heart muscle to weaken and fail. Some forms of pulmonary hypertension are serious conditions that become progressively worse and are sometimes fatal. Although some forms of pulmonary hypertension aren't curable, treatment can help lessen symptoms and improve your quality of life. Symptoms The signs and symptoms of pulmonary hypertension in its early stages might not be noticeable for months or even years. As the disease progresses, symptoms become worse. Pulmonary hypertension symptoms include: - Shortness of breath (dyspnea), initially while exercising and eventually while at rest - Fatigue - Dizziness or fainting spells (syncope) - Chest pressure or pain - Swelling (edema) in your ankles, legs and eventually in your abdomen (ascites) - Bluish color to your lips and skin (cyanosis) - Racing pulse or heart palpitations Causes Your heart has two upper chambers (atria) and two lower chambers (ventricles). Each time blood passes through your heart, the lower right chamber (right ventricle) pumps blood to your lungs through a large blood vessel (pulmonary artery). In your lungs, the blood releases carbon dioxide and picks up oxygen. The oxygen-rich blood then flows through blood vessels in your lungs (pulmonary arteries, capillaries and veins) to the left side of your heart. Ordinarily, the blood flows easily through the vessels in your lungs, so blood pressure is usually much lower in your lungs. With pulmonary hypertension, the rise in blood pressure is caused by changes in the cells that line your pulmonary arteries. These changes can cause the walls of the arteries to become stiff and thick, and extra tissue may form. The blood vessels may also become inflamed and tight. These changes in the pulmonary arteries can reduce or block blood flow through the blood vessels. This makes it harder for blood to flow, raising the blood pressure in the pulmonary arteries. Pulmonary hypertension is classified into five groups, depending on the cause. Group 1: Pulmonary arterial hypertension - Cause unknown, known as idiopathic pulmonary arterial hypertension - A specific gene mutation that can cause pulmonary hypertension to develop in families, also called heritable pulmonary arterial hypertension - Certain drugs - such as certain prescription diet drugs or illegal drugs such as methamphetamines - or certain toxins - Heart abnormalities present at birth (congenital heart disease) - Other conditions, such as connective tissue disorders (scleroderma, lupus, others), HIV infection or chronic liver disease (cirrhosis) Group 2: Pulmonary hypertension caused by left-sided heart disease - Left-sided valvular heart disease, such as mitral valve or aortic valve disease - Failure of the lower left heart chamber (left ventricle) Group 3: Pulmonary hypertension caused by lung disease - Chronic obstructive pulmonary disease, such as emphysema - Lung disease such as pulmonary fibrosis, a condition that causes scarring in the tissue between the lungs' air sacs (interstitium) - Sleep apnea and other sleep disorders - Long-term exposure to high altitudes in people who may be at higher risk of pulmonary hypertension Group 4: Pulmonary hypertension caused by chronic blood clots - Chronic blood clots in the lungs (pulmonary emboli) Group 5: Pulmonary hypertension associated with other conditions that have unclear reasons why the pulmonary hypertension occurs - Blood disorders - Disorders that affect several organs in the body, such as sarcoidosis - Metabolic disorders, such as glycogen storage disease - Tumors pressing against pulmonary arteries Eisenmenger syndrome and pulmonary hypertension Eisenmenger syndrome, a type of congenital heart disease, causes pulmonary hypertension. It's most commonly caused by a large hole in your heart between the two lower heart chambers (ventricles), called a ventricular septal defect. This hole in your heart causes blood to circulate abnormally in your heart. Oxygen-carrying blood (red blood) mixes with oxygen-poor blood (blue blood). The blood then returns to your lungs instead of going to the rest of your body, increasing the pressure in the pulmonary arteries and causing pulmonary hypertension. Risk factors Your risk of developing pulmonary hypertension may be greater if: - You're a young adult, as idiopathic pulmonary arterial hypertension is more common in younger adults - You're overweight - You have a family history of the disease - You have one of various conditions that can increase your risk of developing pulmonary hypertension - You use illegal drugs, such as cocaine - You take certain appetite-suppressant medications - You have an existing risk of developing pulmonary hypertension, such as a family history of the condition, and you live at a high altitude Diagnosis Pulmonary hypertension is hard to diagnose early because it's not often detected in a routine physical exam. Even when the condition is more advanced, its signs and symptoms are similar to those of other heart and lung conditions. To diagnose your condition, your doctor may review your medical and family history, discuss your signs and symptoms, and conduct a physical examination. Doctors may order several tests to diagnose pulmonary hypertension, determine the severity of your condition and find out the cause of your condition. Tests may include: - Echocardiogram. Sound waves can create moving images of the beating heart. An echocardiogram can help your doctor to check the size and functioning of the right ventricle, and the thickness of the right ventricle's wall. An echocardiogram can also show how well your heart chambers and valves are working. Doctors may also use this to measure the pressure in your pulmonary arteries. In some cases, your doctor will recommend an exercise echocardiogram to help determine how well your heart and lungs work under stress. In this test, you'll have an echocardiogram before exercising on a stationary bike or treadmill and another test immediately afterward. This could be done as an oxygen consumption test, in which you may have to wear a mask that assesses the ability of your heart and lungs to deal with oxygen and carbon dioxide. Other exercise tests may also be done. These tests can help determine the severity and cause of your condition. They may also be done at follow-up appointments to check that your treatments are working. - Chest X-ray. A chest X-ray can show images of your heart, lungs and chest. This test can show enlargement of the right ventricle of the heart or the pulmonary arteries, which can occur in pulmonary hypertension. This test can also be used to identify other conditions that may be causing pulmonary hypertension. - Electrocardiogram (ECG). This noninvasive test shows your heart's electrical patterns and can detect abnormal rhythms. Doctors may also be able to see signs of right ventricle enlargement or strain. - Right heart catheterization. After you've had an echocardiogram, if your doctor thinks you have pulmonary hypertension, you'll likely have a right heart catheterization. This test can often help confirm that you have pulmonary hypertension and determine the severity of your condition. During the procedure, a cardiologist places a thin, flexible tube (catheter) into a vein in your neck or groin. The catheter is then threaded into your right ventricle and pulmonary artery. Right heart catheterization allows your doctor to directly measure the pressure in the main pulmonary arteries and right ventricle. It's also used to see what effect different medications may have on your pulmonary hypertension. - Blood tests. Your doctor might order blood tests to check for certain substances in your blood that might show you have pulmonary hypertension or its complications. Blood tests can also test for certain conditions that may be causing your condition. Your doctor might order additional tests to check the condition of your lungs and pulmonary arteries and to determine the cause of your condition, including: - Computerized tomography (CT) scan. During a CT scan, you lie on a table inside a doughnut-shaped machine. CT scanning generates X-rays to produce cross-sectional images of your body. Doctors may inject a dye into your blood vessels that helps your arteries to be more visible on the CT pictures (CT angiography). Doctors may use this test to look at the heart's size and function and to check for blood clots in the lungs' arteries. - Magnetic resonance imaging (MRI). This test may be used to check the right ventricle's function and the blood flow in the lung's arteries. In this test, you lie on a movable table that slides into the tunnel. An MRI uses a magnetic field and pulses of radio wave energy to make pictures of the body. - Pulmonary function test. This noninvasive test measures how much air your lungs can hold, and the airflow in and out of your lungs. During the test, you'll blow into a simple instrument called a spirometer. - Polysomnogram. This test detects your brain activity, heart rate, blood pressure, oxygen levels and other factors while you sleep. It can help diagnose a sleep disorder such as obstructive sleep apnea. - Ventilation/perfusion (V/Q) scan. In this test, a tracer is injected into a vein in your arm. The tracer maps blood flow and air to your lungs. This test can be used to determine whether blood clots are causing symptoms of pulmonary hypertension. - Open-lung biopsy. Rarely, a doctor might recommend an open-lung biopsy. An open-lung biopsy is a type of surgery in which a small sample of tissue is removed from your lungs under general anesthesia to check for a possible secondary cause of pulmonary hypertension. Genetic tests If a family member has had pulmonary hypertension, your doctor might screen you for genes that are linked with pulmonary hypertension. If you test positive, your doctor might recommend that other family members be screened for the same genetic mutation. Pulmonary hypertension classifications Once you've been diagnosed with pulmonary hypertension, your doctor might classify the severity of your disease into one of several classes, including: - Class I. Although you've been diagnosed with pulmonary hypertension, you have no symptoms with normal activity. - Class II. You don't have symptoms at rest, but you experience symptoms such as fatigue, shortness of breath or chest pain with normal activity. - Class III. You're comfortable at rest, but have symptoms when you're physically active. - Class IV. You have symptoms with physical activity and while at rest. Treatment Pulmonary hypertension can't be cured, but doctors can help you manage your condition. Treatment may help improve your symptoms and slow the progress of pulmonary hypertension. It often takes some time to find the most appropriate treatment for pulmonary hypertension. The treatments are often complex and require extensive follow-up care. Your doctor might also need to change your treatment if it's no longer effective. When pulmonary hypertension is caused by another condition, your doctor will treat the underlying cause whenever possible. Medications - Blood vessel dilators (vasodilators). Vasodilators open narrowed blood vessels. One of the most commonly prescribed vasodilators for pulmonary hypertension is epoprostenol (Flolan, Veletri). The drawback to epoprostenol is that its effects last only a few minutes. This drug is continuously injected through an intravenous (IV) catheter via a small pump that you wear in a pack on your belt or shoulder. Potential side effects of epoprostenol include jaw pain, nausea, diarrhea and leg cramps, as well as pain and infection at the IV site. Another form of the drug, iloprost (Ventavis), can be inhaled six to nine times a day through a nebulizer, a machine that vaporizes your medication. Because it's inhaled, it goes directly to the lungs. Side effects associated with iloprost include chest pain - often accompanied by a headache and nausea - and breathlessness. Treprostinil (Tyvaso, Remodulin, Orenitram), another form of the drug, can be given four times a day. It can be inhaled, taken as oral medication or administered by injection. It can cause side effects such as a headache, nausea and diarrhea. - Endothelin receptor antagonists. These medications reverse the effect of endothelin, a substance in the walls of blood vessels that causes them to narrow. These drugs may improve your energy level and symptoms. However, these drugs shouldn't be taken if you're pregnant. Also, these drugs can damage your liver and you may need monthly liver monitoring. These medications include bosentan (Tracleer), macitentan (Opsumit), and ambrisentan (Letairis). - Sildenafil and tadalafil. Sildenafil (Revatio, Viagra) and tadalafil (Cialis, Adcirca) are sometimes used to treat pulmonary hypertension. These drugs work by opening the blood vessels in the lungs to allow blood to flow through more easily. Side effects can include an upset stomach, headache and vision problems. - High-dose calcium channel blockers. These drugs help relax the muscles in the walls of your blood vessels. They include medications such as amlodipine (Norvasc), diltiazem (Cardizem, Tiazac, others) and nifedipine (Procardia, others). Although calcium channel blockers can be effective, only a small number of people with pulmonary hypertension respond to them. - Soluble guanylate cyclase (SGC) stimulator. Soluble guanylate cyclase (SGC) stimulators (Adempas) interact with nitric oxide and help relax the pulmonary arteries and lower the pressure within the arteries. These medications should not be taken if you're pregnant. They can sometimes cause dizziness or nausea. - Anticoagulants. Your doctor is likely to prescribe the anticoagulant warfarin (Coumadin, Jantoven) to help prevent the formation of blood clots within the small pulmonary arteries. Because anticoagulants prevent normal blood coagulation, they increase your risk of bleeding complications. Take warfarin exactly as prescribed, because warfarin can cause severe side effects if taken incorrectly. If you're taking warfarin, your doctor will ask you to have periodic blood tests to check how well the drug is working. Many other drugs, herbal supplements and foods can interact with warfarin, so be sure your doctor knows all of the medications you're taking. - Digoxin. Digoxin (Lanoxin) can help the heart beat stronger and pump more blood. It can help control the heart rate if you experience arrhythmias. - Diuretics. Commonly known as water pills, these medications help eliminate excess fluid from your body. This reduces the amount of work your heart has to do. They may also be used to limit fluid buildup in your lungs. - Oxygen. Your doctor might suggest that you sometimes breathe pure oxygen, a treatment known as oxygen therapy, to help treat pulmonary hypertension, especially if you live at a high altitude or have sleep apnea. Some people who have pulmonary hypertension eventually require continuous oxygen therapy. Surgeries - Atrial septostomy. If medications don't control your pulmonary hypertension, this open-heart surgery might be an option. In an atrial septostomy, a surgeon will create an opening between the upper left and right chambers of your heart (atria) to relieve the pressure on the right side of your heart. Atrial septostomy can have serious complications, including heart rhythm abnormalities (arrhythmias). - Transplantation. In some cases, a lung or heart-lung transplant might be an option, especially for younger people who have idiopathic pulmonary arterial hypertension. Major risks of any type of transplantation include rejection of the transplanted organ and serious infection, and you must take immunosuppressant drugs for life to help reduce the chance of rejection. Lifestyle and home remedies Although medical treatment can't cure pulmonary hypertension, it can lessen symptoms. Lifestyle changes also can help improve your condition. Consider these tips: - Get plenty of rest. Resting can reduce the fatigue that might come from having pulmonary hypertension. - Stay as active as possible. Even the mildest forms of activity might be too exhausting for some people who have pulmonary hypertension. For others, moderate exercise such as walking might be beneficial - especially when done with oxygen. But first, talk to your doctor about specific exercise restrictions. In most cases, it's recommended that you not lift heavy weights. Your doctor can help you plan an appropriate exercise program. - Don't smoke. If you smoke, the most important thing you can do for your heart and lungs is to stop. If you can't stop smoking by yourself, ask your doctor to prescribe a treatment plan to help you quit. Also, avoid secondhand smoke if possible. - Avoid pregnancy and birth control pills. If you're a woman of childbearing age, avoid pregnancy. Pregnancy can be life-threatening for both you and your baby. Also avoid using birth control pills, which can increase your risk of blood clots. Talk to your doctor about alternative forms of birth control. If you do become pregnant, it's important to consult with your doctor as pulmonary hypertension can cause serious complications to both you and the fetus. - Avoid traveling to or living at high altitudes. High altitudes can worsen the symptoms of pulmonary hypertension. If you live at an altitude of 8,000 feet (2,438 meters) or higher, your doctor might recommend that you move to a lower altitude. - Avoid situations that can excessively lower blood pressure. These include sitting in a hot tub or sauna or taking long hot baths or showers. These activities lower your blood pressure and can cause fainting or even death. Also avoid activities that cause prolonged straining, such as lifting heavy objects or weights. - Follow a nutritious diet and stay at a healthy weight. Aim to eat a healthy diet of whole grains, a variety of fruits and vegetables, lean meats and low-fat dairy products. Avoid saturated fat, trans fat and cholesterol. It's likely your doctor will recommend limiting the amount of salt in your diet. Aim to maintain a healthy weight. - Ask your doctor about medications. Take all your medications as prescribed. Ask your doctor about any other medications before taking them, as some can interfere with your medication or worsen your condition. - See your doctor at follow-up appointments. Your doctor may recommend regular follow-up appointments. Let your doctor know if you have any questions about your condition or medications you're taking, or if you have any symptoms or side effects from your medications. If pulmonary hypertension is affecting your quality of life, ask your doctor about options that could improve your quality of life. - Get vaccines. Your doctor may recommend getting an influenza and pneumonia vaccine, as these conditions can cause serious issues for people with pulmonary hypertension. - Get support. If you're feeling stressed or worried due to your condition, get support from family or friends. Or, consider joining a support group with others who have pulmonary hypertension. 

Answer: With Pulmonary hypertension, blood pressure in the pulmonary arteries is  increased because the walls of the pulmonary arteries stiffen and thicken. These changes make it harder for blood to flow, which raises the blood pressure in the pulmonary arteries.