Prospective Echocardiography Assessment of Pulmonary Hypertension and Its Potential Etiologies in Children With Sickle Cell Disease††Conflicts of interest: Dr. Gordeuk has received grants from BioMarin Pharmaceutical Inc., Novato, California, and Actelion Pharmaceuticals Ltd., Allschwil, Switzerland, and is a consultant for Ikaria Holdings, Clinton, New Jersey.