What is pediatric PH

Pediatric PH shares a similar definition to adult PH. It is defined as a resting mean pulmonary artery pressure (mPAP) of greater than 25 mmHg beyond the first three months of life. There are however, key differences in the following disease aspects:

  • Classification,
  • Etiology and symptoms
  • Diagnosis
  • Treatment

Classification

Although the classification of adult and pediatric PH is the same, it is uncertain whether this system is sufficient for use in children. One major reason for this is that pediatric PH is intrinsically linked to issues in lung growth and development and can often be attributed to impaired functional and structural adaptation of the pulmonary circulation during the transition from fetal to postnatal life. In addition, many more conditions have been associated with PH in children compared to adults.

Etiology and symptoms

The majority of pediatric cases are classified as idiopathic PAH (iPAH), heritable PAH, and PAH associated with congenital heart disease (APAH-CHD), marking a difference in the distribution of etiologies in the two populations. Due to non-specific symptoms, iPAH is usually diagnosed in its later stages. Infants with iPAH often present with poor appetite, failure to thrive, tachypnea, and irritability due to low cardiac output. Older children, on the other hand, have similar symptoms to adults including exercise intolerance and occasionally chest pain. Results from the TOPP-1 registry illustrated that near-syncope and syncope were more common in children with iPAH and familial PAH, whereas peripheral edema was more common in adults.

Diagnosis

The non-specificity of PAH symptoms presents difficulties in diagnosing both adults and children. This challenge may be amplified in children due to potential challenges they face in describing and reporting their symptoms. Therefore, it is often necessary to rely on third-party observations. Interestingly, children tend to be diagnosed at an earlier stage of the disease. This is confirmed by results from the US observational REVEAL registry, which showed that adults with iPAH/HPAH or APAH-CHD had a more severe functional class (FC) and poorer hemodynamics than their pediatric counterparts. This has been attributed to the increased exposure of children to upper respiratory tract infections and their increased physical activity, which may lead to the earlier presentation of symptoms.

The proper diagnosis of patients is essential in order to prescribe an appropriate disease management strategy. Recent pediatric registries have shown that a complete evaluation is not carried out as standard in children. A modified and comprehensive diagnostic algorithm, specifically designed for pediatric PH, has been published following the 2013 Nice proceedings by Ivy et al. 2013.