The patient population recruited for this study will include patients being considered for cardiothoracic surgery, as treatment for their cancer, who have evidence of PHTN documented by 2-dimensional and Doppler echocardiography (2D-Echo) uncovered during their pre-operative evaluation for malignancy. Eligible patients include those who have normal LV systolic function with PHTN by Doppler echocardiography, defined as a peak tricuspid velocity of 2.5m/sec or greater without evidence of significant valvular disease. An evaluation for pulmonary hypertension by 2D-Echo will have already been completed by the time the patient is considered for this study.

Inclusion Criteria:

• Age 18 to 85 years old
• Pulmonary Hypertension (PHTN) documented by Doppler echocardiography
• Evidence of underlying lung disease by history and physical and/or chest x-ray and/or pulmonary function testing (PFT's)
• Able to sign informed consent
• Patient being considered for Cardiothoracic Surgery

Exclusion Criteria:

• Patients with clinically significant hypotension (defined as a systolic blood pressure (SBP) <90)
• Active infection/sepsis
• Creatinine greater than 3.0 mg/dl
• LV ejection fraction < 40% (must be done with in the last 30 days prior to signing consent)
• Significant valvular disease as a cause for the PHTN.
• Severe Thrombocytopenia (as defined by platelets less than 20,000) or INR > 1.6
• Hypersensitivity to nesiritide or any of it's components.