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Reduction in pulmonary vascular resistance with long-term epoprostenol (prostacyclin) therapy in primary pulmonary hypertension.

BACKGROUND
Primary (idiopathic) pulmonary hypertension is a progressive, fatal disease. Conventional therapy with anticoagulant and vasodilator drugs may improve symptoms and survival among selected patients, but there is no evidence that the disease can be reversed.


METHODS
We evaluated the effects of long-term therapy (i.e., for more than one year) with intravenous epoprostenol (prostacyclin) in patients with advanced primary pulmonary hypertension. The base-line evaluation included an assessment of pulmonary vascular dilation in response to intravenous adenosine. The epoprostenol dose was increased monthly to the maximum tolerated. Long-term therapy was evaluated by measuring improvement in symptoms, exercise capacity, and hemodynamic measures.


RESULTS
We evaluated 27 patients with primary pulmonary hypertension over a mean (+/-SD) period of 16.7+/-5.2 months. Intravenous adenosine had a variable effect on pulmonary vascular resistance (mean reduction, 27 percent; range, 0 to 56; P<0.001). Epoprostenol therapy was initiated and the rate of infusion was increased by an average of 2.4 ng per kilogram of body weight per minute each month. Twenty-six of the 27 patients had improvement in symptoms and hemodynamic measures, and overall, pulmonary vascular resistance declined by 53 percent to 7.9+/-3.8 resistance units (P<0.001) at the time of restudy. The long-term effects of epoprostenol exceeded the short-term pulmonary vasodilator response to adenosine in all but one patient. Seven of the eight patients who had minimal pulmonary vasodilation in response to adenosine (mean reduction in resistance units, <20 percent) still had a significant reduction in pulmonary vascular resistance when treated with epoprostenol (mean, 39+/-14 percent; P=0.002).


CONCLUSIONS
In primary pulmonary hypertension, long-term therapy with epoprostenol lowers pulmonary vascular resistance beyond the level achieved in the short term with intravenous adenosine. Epoprostenol appears to have sustained efficacy in this disorder.