Effects of Long-term Infusion of Prostacyclin on Exercise Performance in Patients With Primary Pulmonary Hypertension

Study objectives

To determine whether long-term IV prostacyclin (PGI₂) use improves exercise capacity in patients with primary pulmonary hypertension (PPH).

Design

Cycle ergometry and the 6-min walk was used to evaluate the exercise performance of patients with PPH. The patients underwent serial exercise testing after starting continuous IV PGI₂ and were followed up for 19.5 ± 7.5 months. Peak work, peak oxygen consumption (

o₂), peak O₂ pulse, and distance walked in 6 min were used to evaluate performance.

Background

PPH is characterized by medial hypertrophy and intimal proliferation of the pulmonary arterioles, leading to elevation of pulmonary artery pressure, right ventricular failure, and death. Palliative treatment consists of vasodilators, anticoagulants, cardiac glycosides, diuretics, and transplantation. PGI₂, a potent vasodilator and inhibitor of platelet aggregation, has been used for long-term treatment when conventional therapy has been unsuccessful.

Patients

Sixteen patients with PPH (10 women, 6 men; mean age, 24 years).

Results

At the initiation of PGI₂, peak work (± SD) was 35.5 ± 11% of predicted; peak

o₂, 39 ± 10.4%; peak O₂pulse, 5.0 ± 1.7 mL/min; and distance on the 6-min walk, 428 ± 78 feet. At 18 to 27 months, peak work increased to 58.8 ± 23% of predicted (p = 0.001), peak

o₂increased to 52 ± 15% of predicted (p = 0.02), peak O₂ pulse increased to 7.1 ± 3.0 mL/beat (p = 0.004), and performance on the 6-min walk increased to 526 ± 62 feet (p = 0.001). There was a positive correlation between peak

o₂ and peak 6-min walk of 0.6 (p < 0.005) and between peak work and peak 6-min walk of 0.6 (p < 0.005).

Conclusions

Exercise capacity improved in our patients at up to 27 months of follow-up. Exercise testing is helpful in assessing the functional capacity of patients with PPH and may be useful in guiding therapy. Patients who deteriorate while receiving optimal conventional therapy should be considered for IV PGI₂ therapy.