Dr Avitabile: I alluded to some of the differences in adult vs pediatric PH. Many of the differences are related to the developmental origins of pediatric PH. In addition, an understanding of the complex physiology of various types of structural heart disease is essential to understanding PH due to congenital heart disease that may be a result of vascular damage from shunts, multiple levels of pulmonary artery stenosis, pulmonary vein stenosis, or left-sided obstructive disease, among other causes. Pulmonary vasodilators can be problematic in the case of increased pulmonary blood flow or left heart obstruction, but may still be appropriate for use with close observation.
One big challenge in both the clinical care of children with PH and clinical trial design is identifying clinically relevant treatment targets. While the 6MWT is a common test of exercise performance in adults, this is not easily done in children younger than 6 to 8 or in children with developmental delays, orthopedic concerns, or other issues that make ambulation difficult. We are exploring things like actigraphy that may better evaluate physical activity or functional status of children with PH, which will help us identify more appropriate therapeutic outcomes.
Dr Carl: In many ways, we are screening for very different diseases. The following are pediatric conditions that may rapidly progress during the first year of life:
- Alveolar capillary dysplasia
- Surfactant protein abnormalities
- Capillary hemangiomatosis
- Pulmonary veno-occlusive disease
- Congenital pulmonary vein stenosis
- Severe pulmonary hypoplasia
- Massive left to right shunt: arteriovenous malformation
- Infant PH plus congenital heart disease with cardiovascular collapse
- “Idiopathic” neonatal pulmonary hypertension
- Premature closure of the ductus arteriosus
Pulmonology Advisor: What are the ways in which cardiologists and pulmonologists collaborate in the care of these patients?
Dr McGrath-Morrow: Since underlying chronic lung disease is an important cause of secondary PH in children, collaboration between cardiologists and pulmonologists is essential. In addition, other specialists, such as neonatologists and intensivists who frequently treat acute PH exacerbation, should be part of a collaborative team to provide a multidisciplinary approach.
Frequent multidisciplinary meetings and disease-specific PH clinics can help improve outcomes by identifying factors that may be contributing to PH severity and determine best treatment approaches.
Dr Avitabile: Pulmonologists are essential collaborators in the care of children with PH. Many children with PH have developmental lung disease, which results in vascular loss. Children with BPD, congenital diaphragmatic hernia, and other developmental lung diseases may be the fastest growing group of pediatric patients with PH. Many patients have ventilatory failure or insufficiency and are dependent on tracheostomies and ventilators.
The pulmonologists manage the lung disease, the care of which is essential to the vascular disease. Conditions such as reactive airway disease, obstructive sleep apnea, hypoventilation, and gastroesophageal reflux and aspiration can result in increased pulmonary artery pressure and pulmonary vascular resistance, so exceptional care is important.
Dr Carl: Collaboration is essential to improving the understanding and treatment of PH by pediatric cardiologists and pulmonologists who view the etiologies from differing vantage points:
- Delayed and/or maldevelopment of alveoli and vasculature combined with early lung damage create long-term pediatric PH. Primary prevention of chronic lung diseases will need to draw from both disciplines.
- Minimize BPD morbidity by pulmonology/neonatology in conjunction with combined pulmonary and cardiology early detection and therapy.
- Institute therapies to stop proliferation and to improve angiogenesis and alveolarization.
- Both cardiovascular and pulmonary outcomes are needed to define therapeutic response.