Microvascular Blood Flow in Sickle Cell Anemia

Inclusion Criteria: Regadenoson ARM Inclusion Criteria: * Diagnosis of sickle cell anemia confirmed by hemoglobin analysis * Ages 18 to 70 years * Subjects must have laboratory indices as outlined by the protocol * Reliable IV access as determined by physician Sickle Cell Controls ARM Inclusion Criteria: * Diagnosis of sickle cell anemia confirmed by hemoglobin analysis * Ages 18 to 70 years Sickle Cell CEU ARM Inclusion Criteria: * Diagnosis of sickle cell anemia, confirmed by hemoglobin analysis * Males and females age 18-70 years Healthy Control ARM Inclusion Criteria: * African American * Ages 18 to 70 years Technique Optimization Control ARM Inclusion Criteria: -Ages 18 to 70 years Exclusion Criteria: Regadenoson ARM Exclusion Criteria * Hospitalization, emergency department visit or self-reported crisis within last 2 weeks for any reason or 4 weeks from acute chest syndrome * Current physician diagnosis of active asthma (within last 12 months) or current use of asthma medications * Second or third degree AV block or sinus node dysfunction * Known or suspected right to left sided cardiac shunts * History of a bleeding diathesis * History of clinically overt stroke * History of severe hypertension not adequately controlled with anti-hypertensive medications * Receiving chronic anti-coagulation or anti-platelet therapy * History of metastatic cancer * Receiving other investigational study agents, or have received a study agent in the last 30 days * Uncontrolled intercurrent illness * Pregnant or breastfeeding women * Subjects who have a HIV infection * Subjects who have had a hematopoietic stem cell transplant * Subjects who are taking medications that may interact with the investigational agent * Prior hypersensitivity reactions to either regadenoson or ultrasound contrast agents Sickle Cell Controls Exclusion Criteria: * Hospitalization, emergency department visit or self-reported crisis within last 2 weeks for any reason or 4 weeks from acute chest syndrome * Known pregnancy * Known history of HIV * Known or suspected right to left sided cardiac shunts * Receiving other investigational study agents, or have received a study agent within the last 30 days * Subjects who have had a hematopoietic stem cell transplant * Prior hypersensitivity reactions to ultrasound contrast agents * History of severe hypertension not adequately controlled with anti-hypertensive medications * Uncontrolled intercurrent illness Sickle Cell CEU ARM Exclusion Criteria: * Pregnant women * Subjects who have a HIV infection * History of stem cell transplant * Current involvement in a therapeutic clinical trial * Known or suspected right to left sided cardiac shunts * Prior hypersensitivity reactions to ultrasound contrast agents * History of severe hypertension not adequately controlled with anti-hypertensive medications * Uncontrolled intercurrent illness Healthy Control ARM Exclusion Criteria: * Sickle cell disease or sickle cell trait * Known or suspected right to left sided cardiac shunts * Diagnosis of type 1 or type 2 diabetes mellitus * Hypertension * History or current diagnosis of dyslipidemia or taking lipid lowering drugs * Diagnosis of coronary artery disease or peripheral vascular disease * Body weight greater than 10% of ideal weight * Uncontrolled intercurrent illness * Pregnant or breastfeeding women * Subjects who have a HIV infection * Prior hypersensitivity reactions to ultrasound contrast agents Technique Optimization Control ARM Exclusion Criteria: * Known sickle cell disease or sickle cell trait * Known or suspected right to left sided cardiac shunts * Uncontrolled intercurrent illness * Known pregnant or breastfeeding women * Prior hypersensitivity reactions to ultrasound contrast agents