RECENT ADVANCES IN THE TREATMENT OF PEDIATRIC PULMONARY ARTERY HYPERTENSION

Abstract

As our understanding of the pathogenesis of PAH evolves, newer strategies for its treatment are being developed and implemented. Based on studies with adult PPH patients, anticoagulation is now regarded as a mainstay of therapy and is associated with prolonged survival. Before the era of vasodilator therapy, which began in the late 1970s, most children with PPH died within 1 year of diagnosis. Now with chronic calcium channel blockade, survival and QOL are improved in children who acutely respond to vasodilator drug testing. In the author's experience, the 5-year survival rate for patients treated with chronic oral calcium channel blockade who respond acutely to vasodilator testing is 97% versus 35% for those who do not respond acutely. Continuous i.v. prostacyclin has also been used successfully, with a 5-year survival rate of 92% in children in whom oral calcium channel blockade failed (although in some patients the prostacyclin therapy was used as a bridge to transplantation) versus 29% in children in whom oral calcium channel blockade also failed and for whom chronic prostacyclin was unavailable. Before the availability of long-term prostacyclin therapy, 30% to 40% of patients with PPH died while waiting for transplantation. Prostacyclin has virtually eliminated this situation. The results of lung transplantation for adult patients with PPH at 3 years are similar to the results of those on continuous i.v. prostacyclin. Ultimately, the best therapy for an individual child depends on the results of longer follow-up studies. Inhaled nitric oxide has also been used to treat PAH in newborns and other forms of acute and chronic PAH. Although less experience exists with long-term inhaled nitric oxide than with long-term prostacyclin, the preliminary results of long-term inhaled nitric oxide are promising and await further study. The "optimal" vasodilator for long-term therapy, (e.g., calcium channel blockade), prostacyclin, nitric oxide, or potential future therapies, such as prostacyclin analogs, endothelin receptor blockers and thromboxane synthase inhibitors or receptor blockers, must be based on a thorough evaluation with acute vasodilator testing and overall risk-benefit considerations for the various therapeutic regimens. Further clarification of the mechanisms of the development and perpetuation of the PAH process will undoubtedly lead to a refinement in treatment strategies for patients with PAH, which not too long ago was often considered untreatable and fatal. By increasing our understanding of the pathogenesis and pathophysiology of primary and secondary PAH disorders, one day we may be able to prevent or cure these diseases as opposed to providing only palliative therapy. Despite this, therapeutic advances have significantly improved the outcome for children with PAH.