Pharmacotherapy of Pulmonary Hypertension

Abstract

Pulmonary arterial hypertension is a serious disease with significant morbidity and mortality. While it can occur idiopathically, it is more commonly associated with other cardiac or lung diseases. While most of the available therapies were tested in adult populations, and most therapies in children remain off-label, new reports and randomized trials are emerging that inform the treatment of pediatric populations. This review discusses currently available therapies for pediatric pulmonary hypertension, their biologic rationales, and evidence for their clinical effectiveness. KeywordsPulmonary hypertension; Pulmonary vasculature; Vasodilator; Nitric Oxide; Phosphodiesterase; Prostacyclin; Endothelin NORMAL PULMONARY VASCULAR TRANSITIONDuring fetal life, the placenta serves as the organ of gas exchange, and the fetal circulation uses a series of adaptive mechanisms to maximize delivery of oxygen to metabolically active organs such as the brain, gut and kidney. The most highly oxygenated blood enters the fetus via the umbilical vein. To efficiently direct oxygenated blood to the systemic circulation and minimize oxygen loss, almost 90% of fetal blood flow is diverted past the lungs through anatomic shunts through the foramen ovale and the ductus arteriosus. While the lung rapidly grows its network of small pulmonary arteries during the second half of gestation [1], blood flow in the pulmonary circulation remains highly restricted by hypoxic pulmonary vasoconstriction of small pulmonary arteries, which is reversed at birth by the sudden increase in lung oxygenation when the newborn takes his or her first breath. After birth, the first few breaths induce a rapid decrease in pulmonary vascular resistance and increase in pulmonary vascular flow in response to lung expansion, increased oxygen tension, and increased pH. Pulmonary artery pressure and vascular resistance decrease more slowly, with pulmonary arterial pressure reaching its nadir ~2-3 weeks after birth. However, the responsiveness to hypoxia is retained into adulthood, and pulmonary hypertension can be easily triggered in the newborn period by hypoxic lung disease, apnea, or other causes.© 2012 Elsevier Inc. All rights reserved. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptPediatr Clin North Am. Author manuscript; available in PMC 2013 October 01. DEFINITION AND CLASSIFICATION OF PEDIATRIC PULMONARY HYPERTENSIONPulmonary hypertension is necessary to support gas exchange in the fetus, but if pulmonary arterial pressure is elevated after birth or during infancy or childhood,...