1. University of Maryland School of MedicineDepartment of Cardiovascular MedicineBaltimoreMDUSA
2. University of Maryand School of MedicineDepartment of Pulmonary MedicineBaltimoreMDUSA
3. United Therapeutics CorporationResearch Triangle ParkNCUSA
4. Northwestern Memorial HospitalChicagoILUSA
5. North Carolina State UniversityRaleighNCUSA