Pulmonary hypertension (PH) is a disease where there is too much pressure inside the blood vessels that carry blood from the heart to the lungs. The right side of the heart pumps blood to the lungs. Here, the blood picks up oxygen before it returns to the left side of the heart and is pumped out to the body. If these blood vessels from the right heart to the lungs have pressure that's too high, the right side of the heart has to work harder to pump blood and can be damaged over time. PH affects people of all ages and can have a significant impact on quality of life.
Pediatric pulmonary hypertension is PH that occurs in infants and children. Pediatric PH is similar to adult PH but has several differences, including its causes and which treatments are most effective. Managing PH, especially in children, requires a multidisciplinary team to provide medical care, physical therapy, and nutritional guidance. The team should also include a lung specialist who specializes in PH.
Pediatric PH is often caused by heart defects and problems with lung development in the womb. It can also be caused by problems that can occur during or shortly after birth. Pediatric PH involves problems with the heart, lungs, or blood vessels, and it can be caused by other medical conditions as well.
Specifically, congenital heart disease (including heart defects), congenital lung disease (such as bronchopulmonary dysplasia), diseases that affect development (such as Down syndrome), and anatomic abnormalities (like congenital diaphragmatic hernia) can all cause pediatric PH.
Pulmonary arterial hypertension (PAH) is a specific type of PH where people have narrowing of the pulmonary artery (the blood vessel from the right heart to the lungs). PAH causes blood flow to back up into the right side of the heart and down into all of the body’s veins. This can lead to right-sided heart failure and damage to organs such as the liver.
Pediatric (and adult) PH is broken down into five groups based on the condition’s underlying cause. Here is a brief overview of PH groups, including some of the more common causes of PH.
Group 1 is the most common. It includes all types of PAH:
Group 1 also includes persistent pulmonary hypertension of the newborn.
Group 2 PH is caused by diseases of the left side of the heart. In these conditions, the heart cannot pump blood out to the body properly. As a result, blood backs up into the heart and increases the pressure in the blood vessels to the lungs. Left-sided heart diseases causing PH include:
Group 3 PH is caused by low oxygen levels (hypoxia or hypoxemia). In adults, this can be due to lung disease, sleep apnea, or living at high altitudes. In children and infants, this can be due to developmental lung diseases.
Group 4 PH is known as chronic thromboembolic pulmonary hypertension. In this group, PH is caused by blood clots inside the blood vessels of the lungs. These blood clots block the flow of blood and increase blood pressure. Surgery to remove blood clots is a treatment option for this type of PH.
Group 5 PH is caused by other diseases or factors such as:
In addition to groups based on the cause of PH, there are four functional classes that describe the severity of PH symptoms:
Pediatric PH is typically caused by developmental problems affecting the lungs and heart, risk factors that occur before birth, and conditions that occur at birth. PH can occur due to unknown causes (idiopathic), inherited gene mutations (hereditary), heart and lung defects present at birth, and genetic disorders. Types and subtypes of PH are grouped based on their underlying cause.
The diagnosis of PH in children is complicated. PH is often misdiagnosed as another disorder because it is rare and the symptoms are not specific. Getting a diagnosis can sometimes take years. It involves a doctor taking a thorough medical history and performing a careful physical exam. It also involves many diagnostic tests — electrocardiograms, echocardiography, CT/MRI scans, cardiac catheterization, tests for heart and lung function, blood tests, and sometimes sleep studies. The same tests used for diagnosis are also used to track response to treatment and follow disease progression.
Getting an accurate and specific diagnosis — and a baseline of how well the heart and lungs currently work — is necessary before treatment can begin. Different types of PH can respond differently to treatments; the wrong treatment can be ineffective or even harmful.
Gathering a complete medical history and performing a thorough physical exam are the first steps to diagnosing pediatric PH. A family history of PH can hint at heritable PAH. Physical exam findings can help uncover medical conditions contributing to the development of PH.
An electrocardiogram (ECG or EKG) tests the heart’s electrical signals to see how well it is beating. Abnormalities found with an ECG can indicate problems with heart function in specific parts of the heart.
The main tool to study the heart in pediatric PH is an echocardiogram. The echocardiogram is a detailed ultrasound of the heart. It can measure heart function and be used to diagnose heart disorders. Echocardiograms measure blood flow, heart size, and how the heart is beating and moving.
There are two types of echocardiograms that may be used: transthoracic echocardiograms and transesophageal echocardiograms. Transthoracic echocardiograms use a transducer placed on the surface of the chest and abdomen. Transesophageal echocardiograms use a probe placed down the throat (with sedation).
Echocardiograms can examine how well the heart is pumping, assess heart valve function, find heart defects, and even measure blood pressure in major vessels. After diagnosis, echocardiography can be used to track whether the PH is getting better or worse and whether it is responding to treatment.
Imaging tests for PH can include chest X-rays, CT scans, and MRI scans. These tests can check for causes of PH, such as blood clots, disorders of the blood vessels, and lung disease. A ventilation/perfusion scan may be used to examine airflow and blood flow in the lungs and to look for blood clots, but this is less likely to be used in children.
The best test to diagnose PH is cardiac catheterization. It is a more difficult and more invasive procedure than an echocardiogram. While the person is sedated, a long, thin tube (catheter) is inserted through blood vessels in the neck, groin, or the chest and into the heart. Using fluoroscopy (a live X-ray) to guide them, cardiologists can measure heart function, blood flow, and oxygen levels. They can also treat conditions like blocked vessels, stuck valves, and abnormal heart rhythms.
Cardiac catheterization can be repeated after the diagnosis of PH to assess how the disease is progressing and if treatment is working. A special and important test done during cardiac catheterization is called acute vasoreactivity testing (AVT). AVT tests how well the blood vessels can expand when exposed to certain medications. This can help doctors know how severe a person’s condition is and whether certain medications, like calcium channel blockers, will work. AVT can also help determine when heart surgery should be performed.
Heart and lung function in PH can be tested with the six-minute walk test (depending on age) and lung function tests. The six-minute walk test is a type of exercise test. It monitors symptoms and oxygen levels while someone walks on a treadmill, or sometimes even in a hospital corridor. This test is used to determine the functional class (or severity) of PH. It can also evaluate oxygen levels on exertion to determine if the person needs oxygen therapy.
Lung function testing (also called spirometry) measures how well a person can exhale air from the lungs. Spirometry looks for problems involving the lungs that can cause PH.
There are no specific blood tests for pediatric or adult PH. In addition to tests for liver and kidney function, blood tests for pediatric PH look for signs of heart failure, low oxygen, or other conditions that can cause PH. Common blood tests can measure:
Other tests may be used to evaluate and help diagnose pediatric PH. Polysomnography (sleep study) is used to observe oxygen levels and heart and lung function during sleep. Sleep studies are used especially if sleep apnea is suspected or if PAH treatments are not working. Additional blood tests include genetic testing and tests for blood clotting disorders and inflammation.
Pediatric PH is diagnosed based on specific levels of blood pressure in the pulmonary artery measured during cardiac catheterization or echocardiogram. Pediatric PH is diagnosed if the mean pulmonary arterial pressure (mPAP) is 20 mm Hg or higher in children over 3 months of age at sea level.
Treatments for pediatric PH vary based on the type and cause of PH. Pediatric PH treatments typically involve a combination of oxygen therapy and medications. These include types of medications called calcium channel blockers (blood pressure pills), disease-modifying medications, diuretics (water pills), and anticoagulants (blood thinners). Advanced PH can cause significant lung and heart damage. It may require surgery, a lung transplant, or a heart transplant.
Pediatric PH should be treated early to slow or stop the worsening of the disease. If PH is caused by another condition, such as thyroid disease, treating that condition is key.
Children and infants with PH should also receive all age-appropriate vaccines, especially those against influenza, pertussis, and pneumonia. They should have immediate medical attention for any lung-related illnesses. Their growth and development should be carefully monitored. Children with PH should participate in light to moderate cardio exercises but avoid strenuous activities.
Extra (supplemental) oxygen is given to children with PH if the level of oxygen in their blood is too low. Children with an underlying lung disease may especially benefit from extra oxygen. Some children may require oxygen only during physical activity or at night, while others may require it constantly. Oxygen therapy can be useful for children with oxygen levels less than 92 percent.
Children with PH with a good acute vasoreactivity response test who have PH severity of Class 1, 2, or 3 can be treated with calcium channel blockers. A good vasoreactivity response test indicates good response to medications.
Calcium channel blockers work by widening the child’s blood vessels, helping reduce blood pressure. These drugs also help the heart to not have to work as hard, which reduces future strain and damage to the heart. Some calcium channel blockers can also lower the heart rate and prevent certain improper heart rhythms, helping reduce the work done by the heart.
In children, calcium channel blockers may only work for a limited time, so repeated vasoreactivity testing is required to see if the drug is still helping. Calcium channel blockers used in PH include Cardizem (diltiazem) and Procardia (nifedipine).
Targeted therapies may widen blood vessels to increase blood flow and lower blood pressure. They can also help prevent scarring and thickening of blood vessels. Targeted therapies for PH include prostacyclins, endothelin receptor antagonists, phosphodiesterase-5 (PDE-5) inhibitors, and soluble guanylate cyclase stimulators.
Prostacyclins are used to treat PAH (PH Group 1). Prostacyclins, such as Flolan (epoprostenol) and Remodulin (treprostinil), open up blood vessels in the lungs. Prostacyclins are typically given as an injection, but they can be given as an inhaled medication as well.
Endothelin receptor antagonists, such as Tracleer (bosentan) and Letairis (ambrisentan), increase heart function, improve PH symptoms, and delay disease progression. They work by blocking chemicals in the body responsible for narrowing or constricting blood vessels.
PDE-5 inhibitors, such as sildenafil, widen or dilate the blood vessels and help prevent scarring and thickening. They are not recommended for children under 1, and high doses should not be used in children.
Soluble guanylate cyclase stimulators also help widen or dilate the blood vessels. Drugs such as Adempas (riociguat) can measurably improve symptoms and heart function in children with PAH.
Blood thinners, such as Coumadin (warfarin), are sometimes used to treat pediatric PH when there is excessive blood clotting, or in children with high-risk idiopathic or heritable PAH. Blood thinners are risky in children with high risk of falling due to their age or other medical conditions, as they may cause significant bleeding.
Diuretics, or water pills, help lower blood pressure by getting rid of excess water (via urination). Most diuretics are not usually used to treat PH in children, but one drug, Aldactone (spironolactone), has been shown to help.
The prognosis of pediatric PH can vary greatly based on the type and severity of PH. In general, children fare better than adults with PH. Unfortunately, there are not as many studies about PH in children as there are in adults, so less is known about the disease and its treatments.
The good news is that with therapies and specialized care, survival rates of children and infants with PH have improved dramatically. The outlook for PH due to other diseases will depend on the outlook for that disease. PH without an apparent cause has a worse prognosis than the other types. This type of PH is progressive and must be treated aggressively to improve outcomes.
Research into the causes of PH and the best ways to treat PH are ongoing. Science and medicine do not have all the answers, but they are searching for them.
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