In the past decade, three classes of medications have been approved for the treatment of
pulmonary arterial hypertension. A review of the clinical trial data for the prostanoids,
endothelin antagonists, and phosphodiesterase-5 inhibitors has shown that all agents have
similar efficacy on the 6-min walk distance over 12 to 16 weeks, which was the primary end
point in the randomized clinical trials. However, little is known about their long-term efficacy
or about how these drugs affect the underlying disease, if at all. Successful therapy is …