Pulmonary Hypertension

What is pulmonary hypertension?

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.

With pulmonary hypertension, the small arteries in the lung become narrowed or blocked. The heart therefore has to work harder to push the blood through the narrower passageways in the lungs, creating a higher pressure within the pulmonary artery. This higher pressure is pulmonary hypertension.

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.

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 – keep reading for more information.

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

How 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.

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.