by Phyllis Hanlon, Contributing Writer

Despite recent advances made in the understanding of pediatric pulmonary vascular disease (PVD) and pediatric pulmonary hypertension (PH), clinical care decisions are still limited by the lack of studies in these areas. A group of pediatric pulmonary researchers set out to look at what is currently known about the multiple factors related to pediatric PVD and effective ways to identify the underlying causes and triggers, and to determine the best treatment options and discuss long-term outcomes. (https://www.ncbi.nlm.nih.gov/pubmed/28680562)

Causes and Classification

Kara N. Goss, M.D., the lead author of the review, led the discussion by pointing out some differences between pediatric and adult PVD, especially when it comes to lung development. While the lungs are still growing, injury during critical times might have a long-term impact on PVD in childhood. Genetic factors — such as Down syndrome — or environmental factors — such as inflammation or infection — could contribute to the development of PVD. If a baby is exposed to tobacco or drugs or if the mother develops preeclampsia (a condition characterized by high blood pressure and large amounts of protein in the urine during pregnancy), there could also be a greater risk of developing PVD.

Despite these differences, the definition and classification of PH in pediatrics is very similar to that of adults. The review authors did point out, however, that the pediatric task force of the Pulmonary Vascular Research Institute (PVRI) (https://pvrinstitute.org/en/professionals/) created a special classification system (the Panama Classification System) for pediatric patients. The authors noted that, even though the intentions of the special classification system were good, and helped identify the many potential causes of pediatric PVD, the system is somewhat complicated and needs to be modified to be a more useful tool for physicians.

Prevalence

Overall, pediatric PVD is quite rare. To gain some basic understanding of the how often pediatric PVD occurs, the authors looked at several registries and found that PH as a general condition occurs in approximately 64 out of one million children. Idiopathic pulmonary arterial hypertension (IPAH) was found in 0.7 cases per million and the rate of PAH associated with congenital heart disease (CHD) was slightly higher at 2.2 cases per million. They also found that pediatric patients have a better survival rate since drugs specifically designed to treat PAH have come on the market. One source, a Spanish PH registry, (http://www.ucsfcme.com/2011/slides/MPD11002/26DelCerroMaria.pdf) studied several forms of PH and provided a wealth of knowledge about the disease as it relates to survival, including how and how frequently it presents; how the functional class affects the patient; and in which World Health Organization (WHO) group the patients fall. The authors wrote that this registry “…provides a more accurate picture of the nature of pediatric PVD.”

After reviewing the various registries, the authors found some discrepancies in the findings. They believe it’s important to continue to develop “high quality patient registries” to help researchers understand different types of PH, how they develop and respond to drugs, how they affect children as they enter adulthood and the possible long-term effects. Most important, to maximize outcomes for children with PVD, clinical data related to each case should be shared so that age-appropriate diagnostic and monitoring methods and interventions can be established.

Screening

Dr. Goss and her colleagues reported that currently the most frequent way to screen for PH-related diseases in children is with echocardiography. But they pointed out that this technique sometimes fails to accurately diagnose or recognize other abnormalities involving the heart and lungs. Cardiac catheterization is generally recommended for formal diagnosis, although there are risks involved, according to the authors. As many pediatric patients have PH secondary to lung disease, high resolution computed tomography (HRCT) scanning can be helpful in looking at the extent of disease in the lung tissue. Additionally, magnetic resonance imaging (MRI) of the chest could also be used more frequently, after further study, to examine PH patients, the authors added.

Once a definitive diagnosis is made, the most appropriate treatment can be started. The review indicated that specific drugs for PH diseases could be given, although this should be considered only after any underlying disease is successfully managed. Research continues to expand the number and types of therapies that could someday be used in pediatric PH patients. Researchers are thinking more creatively, even beginning very early with stem cells in PH due to lung diseases associated with premature birth. The authors reported that some early animal studies showed that stem cell therapy could “…promote lung repair and regeneration…” These studies were conducted in animals though, not human subjects. But they wrote, “…how stem cell therapies can be utilized to restore pulmonary vascular growth in infants with PVD remains an area of ongoing inquiry, but has potential as a therapeutic breakthrough.”

Outcomes

When it comes to the long-term outcomes for children with PH-related illnesses, the authors asserted that the goal is to “ …maintain growth and development as well as RV (right ventricular) function well into adulthood…” but finding an effective way to do that is still unclear.

“We recognize that there are many potential causes of pediatric pulmonary vascular disease, and treatments that are beneficial for one type may be detrimental for another type,” said Dr. Goss. “Our goal is to use the clinical history, exam, diagnostic tests, and lab studies to best identify the cause. Then and only then, we can determine the best treatment approaches and hopefully improve long term outcomes.”

Kara Goss, M.D. was the recipient of the 2015 Joel Belt Pediatric PH Research and Mentoring Grant, a Barst Fund Award made possible through a generous donation to PHA from Josh and Lindsey Belt in honor of their son Joel, a pediatric PH patient.

Each PH patient is different. It is essential that you talk to your own doctor about what treatment options are best for you. For more information on finding a doctor or an accredited care center, visit https://www.phassociation.org/PHCareCenters/Patients.