Prevalence and risk factors of elevated pulmonary artery pressures in children with sickle cell disease

OBJECTIVES. The objectives of this study were ( 1) to determine the prevalence and risk factors of elevated pulmonary artery pressures in children with homozygous SS or S beta(0) thalassemia using Doppler echocardiography and ( 2) to determine a correlation between abnormal transcranial Doppler examinations and elevated pulmonary artery pressures. METHODS. Screening echocardiograms were prospectively performed during an annual comprehensive clinic visit on children who were older than 6 years and had homozygous SS or S beta(0) thalassemia. Detailed history, examination, and laboratory tests were done, and transcranial Doppler examinations were obtained in children 2 to 14 years of age. Pulmonary hypertension was defined as pulmonary artery systolic pressure of at least 30 mm Hg corresponding to a peak tricuspid regurgitant jet velocity of >= 2.5 m/second. Mild pulmonary hypertension was defined as tricuspid regurgitant jet velocity >= 2.5 to 2.9 m/second. Moderate pulmonary hypertension was defined as tricuspid regurgitant jet velocity >= 3 m/second. Patients with pulmonary stenosis or right outflow obstruction were excluded. Characteristics were compared between patients with mild, moderate, and no pulmonary hypertension using 1-way analysis of variance for continuous variable and Fisher's exact test for categorical variables. RESULTS. Of the 75 patients who had homozygous SS/S beta(0) thalassemia and were older than 6 years, echocardiograms were obtained for 62 ( 82.6%). Thirty percent ( 19 of 62) of patients had elevated tricuspid regurgitant jet velocity >= 2.5 m/second. One third of these patients had tricuspid regurgitant jet velocity >= 3 m/second. All patients with elevated tricuspid regurgitant jet velocity had SS disease. A high reticulocyte count, low oxygen saturation, and a high platelet count were significantly associated with elevated pulmonary artery pressures. There was no difference in age, gender, history of acute chest syndrome, hydroxyurea therapy, chronic blood transfusion, stroke, hemoglobin, and bilirubin between patients with and without elevated pulmonary artery pressures. A total of 47% patients with elevated tricuspid regurgitant jet velocity and 57% without elevated tricuspid regurgitant jet velocity had screening transcranial Doppler examinations. Transcranial Doppler examinations were normal for all patients. CONCLUSIONS. High pulmonary artery pressures do occur in children with sickle cell disease. Screening by echocardiography can lead to early detection and intervention that may potentially reverse this disease process. There was no correlation between elevated pulmonary artery pressures and abnormal transcranial Doppler examination in our study.