The purpose of this study is to use cardiac magnetic resonance imaging (CMR) and echocardiographic tissue Doppler imaging to demonstrate a unique restrictive cardiomyopathy of sickle cell disease. The investigators will characterize its frequency and how it might change (e.g., presence/absence and severity) over a 2-year period.

Sickle cell disease (SCD) causes progressive cardiopulmonary morbidity, beginning in childhood, which can ultimately be fatal. As a group, cardiopulmonary complications, such as acute chest syndrome and sudden death, are now the most common causes of death in SCD, especially in adolescents and adults.

Patients with SCD have features of both an anemia-related, high cardiac output state and a restrictive cardiomyopathy (RCM). The investigators propose that this unique RCM is an overlooked and understudied complication of SCD. RCM could explain the modest increases in pulmonary artery pressure in patients with SCD, as measured by cardiac catheterization or estimated by tricuspid regurgitant jet velocity (TRJV), which has often been attributed to a primary pulmonary arterial hypertension (PAH). RCM could also be the cause of unexplained sudden cardiac death in SCD, which is a feature of other forms of RCM.

The investigators overarching hypothesis is that increased reactive oxygen species (ROS)-mediated angiotensin-1 receptor (AT1R)-TGFβ1 signaling is pro-fibrotic and, in combination with vaso-occlusive ischemia-reperfusion injury, results in an age-dependent, progressive RCM that can be detected by non-invasive cardiac imaging.

This pilot, longitudinal, observational study uses a novel, comprehensive, multimodal cardiac imaging strategy, combining cutting-edge cardiac magnetic resonance imaging (CMR) and echocardiographic tissue Doppler imaging (TDI), to demonstrate the unique RCM of SCD, characterizing its frequency and the temporal evolution over a 2-year period. The investigators will also correlate the RCM phenotype with biomarkers of ROS and renin angiotensin system (RAS)-TGFβ1 signaling.

This research could change the investigators understanding of how SCD affects the heart and lungs. The investigators propose studies that will change the current concept of primary pulmonary vasculopathy to a cardiomyopathy-centered model with secondary pulmonary vascular changes leading to sudden death. This translational pilot study will deliver a novel, clear, quantifiable CMR phenotype with established diagnostic performance that will be used in phase II/III clinical trials to test anti-fibrotic therapy to prevent or reverse SCD-related RCM.

Inclusion Criteria:

• Sickle cell anemia (HbSS) or sickle-β°-thalassemia (HbSβ°) confirmed by hemoglobin separation and identification techniques
• Ability to cooperate with and undergo CMR without sedation or anesthesia.
• Ability to cooperate with and undergo echocardiogram
• Written informed consent in accordance with the institutional policies and federal guidelines must be provided by the participant (if ≥18 years of age) or parent or legally authorized guardian (if the participant is <18 years of age) Minor participants ≥11 years of age will be requested to provide assent

The following additional inclusion criterion applies to Age Stratum A:

Age 6 to 13.99 years

The following additional inclusion criteria apply to Age Stratum B:

• Age 14 to 20.99 years
• Detectible and quantifiable TRJV with reported value

The following additional inclusion criteria apply to Age Stratum C:

• Age ≥21 years
• Detectible and quantifiable TRJV with reported value

The following additional inclusion criteria apply to Stratum D:

• Age ≥6 years.
• Current use of disease-modifying therapy [hydroxyurea, chronic transfusions, or both (given concurrently, sequentially, or both)] that was initiated at <3 years of age, and for which there has been no interruption of therapy for >6 consecutive months since the initiation of disease-modifying therapy.

Exclusion Criteria:

• Any contraindication to MRI or physical or behavioral factor that could degrade the quality of MRI data or interfere with a participant's tolerance of the MRI, such as permanent or semi-permanent metallic implants, including pacemakers and defibrillators, or severe claustrophobia
• Known ventricular septal defect (VSD) documented in medical record
• Estimated Glomerular Filtration Rate (eGFR) <60 mL/min/1.73 m2 (estimated by serum creatinine or cystatin-C)
• Pregnancy (documented by serum or urine pregnancy test)

The following additional inclusion criterion applies to strata A, B and C only:

- Current chronic transfusion therapy (defined as regular, approximately monthly, transfusions of packed red blood cells given for at least 6 consecutive months for the treatment of prevention of SCD-related complications with the plan to continue this therapy at the time of potential enrollment).

Enrolling a maximum of 40 participants in the entire study across four age strata: A, 6 - 13.9 years; B, 14 - 20.9 years; C, 21 years and older; and D, 6 years and older.

AEs were collected for three, separate 30-day intervals over the entire study period of 2 years. Each 30-day interval was defined as starting with the study visit during which annual study activities were performed (e.g., cardiac magnetic resonance imaging [CMR]) and ending 30 days after that study visit. AEs were assessed as they occurred during each study visit, and AEs that occurred in the 30 days after each study visit were collected by scripted phone call from the study team.

All participants in strata A, B and C had severe diffuse myocardial fibrosis. That is, all participants had the phenotype for which we assessed, so correlative studies (e.g., affected vs. non-affected) could not be performed. Therefore, we amended the protocol and opened an additional, fourth stratum (D) to study individuals who were previously not eligible for inclusion.