Pediatric pulmonary arterial hypertension: current and emerging therapeutic options

Role of endothelin in uteroplacental circulation and fetal vascular function

Endothelins are 21-amino acid peptides involved in vascular homeostasis. Three types of peptide have been identified, with endothelin-1 (ET-1) being the most potent vasoconstrictor currently known. Two endothelin receptor subtypes are found in various tissues, including the brain, heart, blood vessel, lung, and placenta. The ETA-receptor is associated with vasoconstriction in vascular smooth muscle. Conversely, the ETB-receptor can elicit a vasoconstrictor effect in vascular smooth muscle and a vasodilator effect via its action in endothelial cells. Both receptors play a key role in maintaining circulatory homeostasis and vascular function. Changes in ET-1 expression are found in various disease states, and overexpression of ET-1 is observed in hypertension and preeclampsia in pregnancy. Placental localization of ET-1 implies a key role in regulating the uteroplacental circulation. Additionally, ET-1 is important in the fetal circulation and is involved in the pulmonary circulation and closure of the ductus arteriosus after birth, as well as fetal growth constriction in utero. ET receptor antagonists and nitric oxide donors may provide therapeutic potential in treating conditions associated with overexpression of ET and hypertension.

Safety and tolerability of targeted therapies for pulmonary hypertension in children

The objective of this study is to evaluate the safety and tolerability of the pharmacological treatment of pulmonary hypertension in pediatric patients. It is a retrospective, longitudinal, observational study on pediatric patients undergoing treatment with pulmonary targeted therapies. 63 patients were included (51% male), with a median age of 3.4 years (IQR, 3.6 months-10 years) and a median weight 13 kg (IQR, 6-30 kg). Congenital heart disease was the etiology of pulmonary hypertension in the majority of cases (n = 33) and 28 patients were in NYHA functional class III-IV. The most commonly used drug was sildenafil (n = 79, 56%), followed by bosentan (n = 27, 23%), and a combination of both (n = 14, 41%). 34 patients had adverse reactions (54%) with an incidence rate of 1.02 per patient per year. The most commonly reported reactions were gastrointestinal symptoms (22%) and spontaneous erections (22%) in males. Nine severe adverse reactions (10%) occurred, requiring eight treatment withdrawal and one hospital admission. Treatment with targeted therapies for pulmonary hypertension is safe in the pediatric population. Severe ADRs were uncommon both in monotherapy and in combination therapy. Combination therapy was associated with a higher rate of ADRs. We observed similar survival rates in children receiving sildenafil doses according to the European Medicines Agency (EMA) recommendations or higher.

Hydralazine in infants with persistent hypoxemic respiratory failure

BACKGROUND

Most deaths of infants with chronic lung disease (CLD) are caused by respiratory failure, unremitting pulmonary artery hypertension (PAH) with cor pulmonale, or infection. Although the exact prevalence of PAH in infants with CLD is unknown, infants with CLD and severe PAH have a high mortality rate. Except for oxygen supplementation, no specific interventions have been established as effective in the treatment for PAH in premature infants with CLD. Little has been proven regarding the clinical efficacy of vasodilators and concerns remain regarding adverse effects.

OBJECTIVES

To review current evidence for the benefits and harms of hydralazine therapy to infants with persistent hypoxemic respiratory failure.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE via PubMed and EMBASE, and other clinical trials registries through November 2011 using the standard search strategy of the Cochrane Neonatal Review Group. We searched these databases using a strategy combining a variation of the Cochrane highly sensitive search strategy for identifying randomised trials in MEDLINE; sensitivity-maximising version with selected MeSH and free-text terms: hydralazine, vasodilator agent, antihypertensive agent, heart diseases, lung diseases, respiratory tract diseases, infant, and randomised controlled trial.

SELECTION CRITERIA

We considered only randomised controlled trials and quasi-randomised trials for inclusion. We included low birth weight (LBW) infants with persistent hypoxemic respiratory failure who were treated with any type of hydralazine therapy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality according to pre-specified criteria.

MAIN RESULTS

We found no studies meeting the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

There was insufficient evidence to determine the safety and efficacy of hydralazine in LBW infants with persistent hypoxemic respiratory failure. Since hydralazine is inexpensive and potentially beneficial, randomised controlled trials are recommended. Such trials are particularly needed in settings where other medications such as sildenafil, inhaled nitric oxide (iNO), or extracorporeal membrane oxygenation (ECMO) are not available.