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What is pulmonary hypertension (PH)?

Pulmonary hypertension (PH) is abnormally high blood pressure that occurs in the arteries of the lungs (the pulmonary arteries). To understand pulmonary hypertension, it’s good to first know how the respiratory and circulatory systems work together. Keep in mind that the left and right sides of the heart have essentially different jobs.

  • When you inhale, you breathe oxygen into your lungs. That oxygen is transferred to blood cells, and that blood (now “oxygenated”) is collected in the left side of the heart.
  • The heart pumps out the oxygenated blood (through the arteries) to supply the rest of the body with oxygen.
  • The blood – now devoid of oxygen – travels back (through the veins) to the right side of the heart.
  • The right side of the heart collects the de-oxygenated blood, and pumps it (through the pulmonary artery) into the lungs.
  • Then the cycle begins again: In the lungs, the blood cells drop off carbon dioxide (for us to exhale), picks up the oxygen that we inhale, and re-collects in the left side of the heart.

Some cases of PH have no identifiable cause (idiopathic pulmonary hypertension). However, genetic defects and immune system disease may be contributing factors to the development of this disease.

Another type of PH, called secondary pulmonary hypertension, occurs when the arteries in the lungs become too narrow for blood to flow through the vessels normally or because there are too few vessels to begin with. As a result, the heart works harder to pump blood through the lungs, causing pressure in the pulmonary artery to rise. Narrowing of the vessels in secondary hypertension can be caused by an associated medical condition such as blood clots, congenital heart defects, and liver disease.

The first symptoms of PH are typically shortness of breath during mild physical activity, although some patients may have fainting spells, especially with exercise. However, because the symptoms of PH aren’t specific to the condition, it can be difficult to diagnose.

While for most patients there is no “cure” for pulmonary hypertension, certain medications can help lessen symptoms and improve lung and heart function. Careful monitoring by a cardiologist can help your child live as normal life as possible.

What are the types of pulmonary hypertension?

Pulmonary hypertension can be grouped into one of two categories, depending on what we know about what is causing it:

Idiopathic pulmonary hypertension (IPH)

  • This diagnosis means that there is no clear cause of your child’s pulmonary hypertension.
  • IPH occasionally runs in families, and sometimes the BMPR2 gene (or another gene) is involved.

Secondary pulmonary hypertension

This diagnosis means that the pulmonary hypertension is thought to be caused by or associated with something else. Possibilities include:

  • some congenital (present at birth) abnormalities of the heart
  • some lung diseases, often related to prematurity
  • diseases that primarily affect other organs, such as scleroderma, some liver diseases, hereditary hemorrhagic telangiectasia, AIDS/HIV, and sickle cell disease
  • abnormal function of the left ventricle
  • chronic thromboembolic disease, in which many small blood clots formed elsewhere travel into the lungs and are lodged there
  • environmental factors, such as exposure to the drugs fenfluramine and dexfenfluramine (Fen-phen) or living at very high altitudes

It’s extremely important to learn whether your child’s PH is idiopathic or secondary, and if secondary, what is causing it — this is how your child’s doctor will determine the treatment plan.

Pulmonary Hypertension | Symptoms & Causes

What are the symptoms of pulmonary hypertension?

Initial symptoms of PH are often minor, but slowly get worse over time. These symptoms can also occur as parts of other diseases, which can make it challenging for doctors to detect PH early. Be sure to consult your doctor if you experience any of the following symptoms.

The most common signs and symptoms of pulmonary hypertension are:

  • shortness of breath while performing everyday activities (walking or climbing stairs)
  • excessive fatigue
  • fainting spells
  • dizziness
  • rapid heart beat
  • low blood pressure
  • swelling of legs and hands

What causes pulmonary hypertension?

Unfortunately, it’s a complicated question. We know that PH occurs when the heart has to work extra hard to move blood through the very small vessels of the pulmonary artery to the lungs, eventually causing the heart muscle to weaken. At the most physical level, this might occur for one or both of two reasons:

There are fewer of these small vessels. This may be because:

  • fewer of them develop as the lung grows
  • they become blocked off by small blood clots
  • they become blocked off by the thickening of the intima (the lining of the artery)

The vessels are smaller than normal in diameter. This may be due to:

  • an increased number and/or size of cells (smooth muscle and other types of cells)
  • connective tissue disorders
  • blood clots that form in the lungs
  • congenital heart defects
  • chronic liver disease
  • sleep apnea

Researchers aren’t sure why these things happen, but many people group together types of PH based on presumed cause.

Pulmonary Hypertension | Diagnosis & Treatments

How do we diagnose pulmonary hypertension?

Measuring pulmonary blood pressure

  • A pediatric cardiologist or other physician will perform a physical examination, listening to your child's heart and lungs.
  • An echocardiogram (a test which uses sound waves to determine and structure and function of the heart) will sometimes, but not always, give an accurate idea of pulmonary artery pressure. This test is painless, takes about 30 minutes, and is easily performed in the doctor's office. In order to get the clearest images possible, it’s important for children to cooperate and hold very still. Children younger than 3 who are restless may be given a medication (a sedative) to help them relax during a length procedure.
  • Cardiac catheterization is a procedure that gives us very detailed information about the structures inside the heart muscle. In some cases, we may need your child to stay overnight in the hospital for this test.

Other tests your child’s doctor may order include:

  • Blood tests may help identify the underlying cause of the pulmonary hypertension as well as related medical conditions that occur as a result of the high blood pressure.
  • CT scans of the chest show the lungs in more detail than a chest x-ray and better detects certain problems.
  • Cardiac MRI is a non-invasive test that shows the structure and function of the heart without the radioactive radiation used in x-rays.
  • Pulmonary function tests measure breathing and lung capacity.
  • Ventilation and perfusion scans: Oxygen and a special type of test medicine is inhaled or injected into a vein in your child’s arm to determine the path of air and blood flow within the lungs.

After all necessary tests are completed, experts at Boston Children’s Hospital meet to review and discuss what they have learned about your child's condition. Then we’ll meet with you and your family to discuss the results and outline the best treatment options.

How we treat pulmonary hypertension

While no cure has been found for secondary or idiopathic pulmonary hypertension, there are several treatments that can decrease pulmonary arterial pressure and improve your child's symptoms.

For idiopathic PH in particular, treatment is aimed at alleviating and controlling symptoms. This may be done using medication. Only in severe cases is surgery needed.

Secondary pulmonary hypertension

The most common types of treatments used for secondary pulmonary hypertension include:

  • Inhaled oxygen to help raise the levels of oxygen in the bloodstream. This may be particularly helpful while sleeping, when your child may breathe less strongly than when he's awake. Oxygen is given by two small tubes in the very front of the nose (“nasal cannula”), and can help your child even when she is walking about.
  • Inhaled nitric oxide (iNO) to relax pulmonary blood vessels. Given just like inhaled oxygen, iNO is typically used in children hospitalized for short-term therapy (usually hours or days) or for testing the pulmonary arteries during heart catheterization.
  • Medications that help to relax pulmonary blood vessels, making it easier for your child's heart to pump blood. These come in several different forms: oral (pill), inhaled, or injected through the skin.
  • Anticoagulants can prevent blood clots in your child's lungs.
  • Diuretics can help your child's kidneys eliminate water.
  • Atrial septostomy may be used in severe cases of pulmonary hypertension if medication fails to control the child's right ventricle from working very hard to pump blood. This surgery is done in the catheterization laboratory. During the procedure, a small hole is created between the upper chambers of your child's heart muscle, redirecting some of the flow of blood past the right ventricle to the left ventricle.
  • A new, experimental form of therapy, called the transvascular Potts procedure, is being pioneered at Boston Children's. In this procedure, a small shunt is placed between the pulmonary artery and the aorta (main artery to the body), to increase blood flow to the heart and lower blood pressure.
  • Lung transplantation may be an option for some patients who do not respond to medication.
How Boston Children’s Hospital approaches pulmonary hypertension

The mission of the Pulmonary Hypertension Program is threefold:

  • Provide the best possible care for our patients. Ours is a multidisciplinary approach using experienced physicians and other clinical professionals who have expertise in specific areas. Your child’s care may also involve consultation with specialists at other institutions, to make sure that we bring the best collective knowledge to each case.
  • Advance our understanding of pulmonary hypertension and develop new therapies. This serves both current and future patients: Our clinical trials regularly bring new treatments to our patients sooner than would be otherwise possible.
  • Train new practitioners. As a program with enormous experience in treating children with pulmonary hypertension, it’s our responsibility to help train the next generation of professionals dedicated to curing this disease.

Pulmonary Hypertension | Research & Clinical Trials

Boston Children’s Hospital is home to the world’s most extensive research enterprise at a pediatric hospital. We also have many partnerships with the top research, biotech, and health care organizations, and we work together to find innovative ways to improve kids’ health.

Thanks to advances in basic science and clinical research, better therapies for pulmonary hypertension are being developed every year.

  • We are a leader in the use of nitric oxide, prostacyclin analogs, endothelin antagonists, and other investigational therapies to treat both idiopathic and secondary pulmonary hypertension in children.
  • Researchers and doctors have conducted a quality of life study for patients with pulmonary hypertension in an effort to identify strategies to improve development.

Current therapeutic trials include:

  • evaluation of a new, more efficient way of delivering inhaled nitric oxide
  • study of the long-term effects of ambrisentan. Used to treat PH, this medicine can help make exercise and breathing easier.

Pulmonary Hypertension | Programs & Services