PROTOCOL ENTRY CRITERIA:

--Disease Characteristics--

Diagnosis of moderate to severe precapillary pulmonary hypertension (New York Heart Association class III/IV) unresponsive to attempted use of chronic oral vasodilators for at least 1 month

Cardiac catheterization at baseline: Pulmonary artery pressure at least 25 mm Hg AND Pulmonary capillary wedge pressure or left ventricular end diastolic pressure no greater than 15 mm Hg AND Pulmonary vascular resistance greater than 3 mm Hg/L/min

Echocardiogram at baseline: Right ventricular hypertrophy or dilation AND Normal left ventricular function AND Absence of mitral valve stenosis

Chest radiograph within prior 3 months Clear lung fields OR Multiple patchy interstitial (not diffuse) lung fields AND At least 1 of the following:

• Right ventricular enlargement
• Prominence of main pulmonary artery
• Enlarged hilar vessels
• Decreased peripheral vessels

No significant parenchymal lung disease within prior 3 months as evidenced by: Total lung capacity no greater than 70% predicted FEV/FVC ratio no greater than 50% Diffuse interstitial fibrosis or alveolitis by high resolution CT if total lung capacity is 70-80% or DLCO less than 60%

No chronic thromboembolic disease with clot proximal to lobar bifurcation

Baseline exercise capacity at least 50 meters walked in six minutes

--Prior/Concurrent Therapy--

Endocrine therapy:

• At least 30 days since prior chronic prostaglandin or prostaglandin analogue therapy (including Flolan IV)
• No concurrent prostaglandins or prostaglandin analogues

Other:

• At least 1 month since prior new type of chronic therapy (e.g., different category of vasodilator, diuretic, digoxin) for pulmonary hypertension, except anticoagulants
• At least 1 week since discontinuation of prior pulmonary hypertension medication, except anticoagulants
• At least 30 days since prior participation in an investigational drug study
• No other concurrent investigational drug
• No concurrent chronic intravenous or inhaled medications (except oxygen)

--Patient Characteristics--

Cardiovascular:

• No portal hypertension
• No left sided heart disease as defined by: Pulmonary capillary wedge pressure or left ventricular end diastolic pressure greater than 15 mm Hg OR LVEF less than 40% by MUGA or angiography OR LV shortening fraction less than 22% by echocardiography OR Symptomatic coronary disease (demonstrable ischemia)

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Mentally and physically capable of using an infusion pump
• HIV negative
• No other disease associated with pulmonary hypertension (sickle cell anemia, schistosomiasis)
• No musculoskeletal disorder (arthritis, artificial leg, etc.) or any disease limiting ambulation, or connected to a nonportable machine
• No concurrent physiological condition contraindicating use of UT-15