Pulmonary Artery Hypertension in Children with Sickle Cell Disease: Is Chronic Transfusion Protective?.

Background Studies in adults with sickle cell disease (SCD) suggest an increased prevalence of pulmonary artery hypertension (PAHTN) with associated increased morbidity and mortality. These findings have not been validated in children. Methods The digital echocardiography (echo) database at Children’s National Medical Center was searched for echos performed on patients with SCD from 1999 to 2006. Patients on chronic transfusions undergo regularly scheduled studies; other patients are referred for a variety of indications including murmurs, cardiomegaly, hypoxia, chest pain, and respiratory distress. Echo reports and digital images were reviewed and the following information was recorded: Chronic transfusion, date of study, blood pressure, cardiac structure, ventricular function, presence of tricuspid regurgitation (TR), and velocity of TR. The estimated right ventricular (RV) pressure was calculated using modified Bernoulli equation (adding 5 mm Hg for estimated right atrial pressure if the inferior vena cava was not dilated). The ratio of RV systolic pressure to systemic systolic blood pressure was calculated. All studies with TR velocities of < 3 m/sec or a RV to systemic ratio of less than one third were considered to be normal. Results: The SCD database has 1060 patients ages 0 to 21 years; 166 echos were performed in 104 routine patients and 72 echos in 47 children while on chronic transfusions. TR could be measured in 56 routine and 20 transfusion studies. Comorbidities were present in 11 studies (7 patients) in the routine group: structural heart disease (4 ), constrictive pericarditis (1 ), significant obstructive airway disease (1 ), and pneumonia requiring mechanical ventilation (1 ). There were no comorbidities in the transfusion group. The mean TR velocity, estimated RV pressure, and RV to systemic pressure ratios were higher in the routine group; however when patients with comorbidities were removed, this difference was no longer statistically significant. | | Routine (n=55) | Routine/no comorbidities (n=44) | Transfused (n=20) | |:---------------------------------------------------------------------------------- | --------------- | ------------------------------- | ----------------- | | 1p = 0.01 transfused vs. routine; p = 0.11 transfused vs. routine/no comorbidities | | 2p < 0.01 transfused vs. routine; p = 0.09 transfused vs. routine no comorbidities | | 3p = 0.01 transfused vs. routine; p = 0.13 transfused vs. routine/no comorbidities | | 1TR velocity (m/sec) | 2.54 ± 0.48 | 2.30 ± 0.30 | 2.30 ± 0.30 | | | Range 1.67–3.93 | Range 1.67–3.19 | Range 1.70–2.76 | | 2RV pressure (mm Hg) | 31.8 ±10.5 | 29.2 ± 6.6 | 26.5 ± 5.6 | | | Range 16.2–67.8 | Range 16.2–45.7 | Range 16.6–36.4 | | 3RV/systemic pressure ratio | 0.29 ± 0.11 | 0.26 ± 0.064 | 0.23 ± 0.065 | | | Range 0.16–0.78 | Range 0.16–0.41 | Range 0.14–0.38 | There were 6 routine studies (2 when patients with comorbidities were removed) and no transfusion studies with a TR velocity above 3.0 m/sec. There were 23 routine studies (18 when patients with comorbidities removed) and 6 transfusion studies with a TR velocity between 2.5 and 3.0 m/sec. The ratio of RV to systemic pressure was greater than one third in 11 routine patients (5 when patients with comorbidities were removed) and 1 transfusion patient. Conclusions PAHTN is present in a small number of children with SCD and may be exacerbated by other medical problems. Chronic transfusion may be protective against PAHTN. Prospective analysis of this population is warranted.