Pulmonary Hypertension in Children and Adolescents with Sickle Cell Disease.

Pulmonary hypertension occurs in 20–40% of adults with sickle cell disease and has a poor prognosis; age of onset and prevalence in childhood are not well established. In adults, recurrent acute chest syndrome is associated with chronic sickle cell lung disease and perhaps pulmonary hypertension. Hematologically normal children with obstructive sleep apnea are at risk for pulmonary hypertension. We sought to determine the prevalence of pulmonary hypertension in children and adolescents with sickle cell disease, explore potential association with abnormal pulmonary function or sleep apnea, and identify other clinical or laboratory factors associated with this potentially life-threatening complication. Forty-eight patients (age 5–21 years, median 12 years) consented to participate. Thirty-eight (79%) had Hb SS; five each had Hb SC and S-beta thalassemia (three beta plus and two beta zero) (10.4%). Eleven (22.9%) were on chronic transfusion (seven for stroke, three for abnormal TCD velocity screening, and one for recurrent pain crises); nineteen (39.5%) were on hydroxyurea (ten for recurrent acute chest syndrome and nine for recurrent pain). A detailed history and physical examination were done on all enrolled subjects (history was comprehensive, but specifically included cardiopulmonary symptoms; neurological problems; number of pain crises and acute chest syndrome; blood transfusions; use of hydroxyurea; and a screening for obstructive sleep apnea). If apnea history was suggestive, polysomnography was done. In addition, all study subjects had Doppler echocardiography and pulmonary function tests (PFT). Pulmonary hypertension was defined as an age and body mass index-adjusted tricuspid regurgitant jet velocity (TRV) of greater than 2.5 mm/sec. Among the study group, 31 (64.5%) had pulmonary function tests; 17 (54.8%) had restrictive abnormalities on PFT, three (9.6%) had obstructive changes and 11 (35.4%) had normal PFT. Three patients (6.2%) had a history suggestive of apnea, then polysomnography; one was normal and two had OSA. Four of the 48 patients (8.3%) had PHT (TRV values 2.52, 2.55, 2.61, and 2.91). All had Hb SS. Two were age 17 and 18 years and two were 10 and 11. All were asymptomatic. One had restrictive PFT and none had OSA. There was no correlation between the presence of PHT and pulmonary function abnormalities or sleep apnea. Of the various other clinical and laboratory parameters examined, only an elevated serum indirect bilirubin was associated with PHT; there was a trend toward association with elevated reticulocyte count and low fetal Hb levels. In summary, the prevalence of PHT our pediatric sickle cell population is 8.3%. As reported in adults, there may be an association between PHT and more severe hemolysis. We could find no association with abnormal pulmonary function or obstructive sleep apnea.