Long Term Follow-Up of Pediatric Sickle Cell Disease Patients with Conditional Velocities on Transcranial Doppler (TCD).

Abnormal TCD defined as high mean maximum velocities > 200 cm/sec are highly predictive of stroke risk and justify long term transfusion program. Outcome and risk factors of conditional TCD defined as velocities 170–200 cm/sec remains to be described. Patients and methods Since 1992, 371 pediatric SCD patients (303 SS, 44 SC, 18 Sß+, 6 Sß0) were systematically explored once a year by TCD. The newborn screened cohort (n=174) had the first TCD exploration between 12 and 18 months of age. TCD was performed with a real-time imaging unit, using a 2 MHz sector transducer with color Doppler capabilities. Biological data were assessed at baseline, after the age of 1.5 years and remotely of transfusion or VOC. We report the characteristics and the outcome in patients (n=43) with an history of conditional TCD defined by mean maximum velocities ranging between 170 and 200 cm/s in the ACM, the ACA or the ICA.

Results: The mean follow-up of TCD monitoring was 5,5 years (0 – 11,8 y). All patients with an history of conditional doppler were SS/Sb0 (n=43). Mean (SD) age of patients at the time of their first conditional TCD was 4.3 years (2.2) whereas in our series the mean age at abnormal TCD (> 200 cm/sec) occurrence was 6.6 years (3.2). Comparison of basal parameters showed highly significant differences between patients with conditional TCD and those with normal TCD: Hb 7g4 vs 8g5 (p<0.001), MCV 82.8 vs 79 (p=0.047). We also had found such differences between patients with normal and those with abnormal TCD (Hb and MCV p< 0.001). Two patients were lost of follow-up. Two patients died during a trip to Africa. Conditional TCD became abnormal in 11/43 patients and justified transfusion program. Mean (SD) conversion delay was 1.8 (2.0) years (range 0.5–7y). No stroke occurred. 16 patients required a treatment intensification for other indications (frequent VOC/ACS, splenic sequestrations): 6 were transplanted and 10 received HU or TP. Significant risk factors (Pearson) of conversion to abnormal were the age at time of conditional TCD occurrence < 3 y (p<0.001), baseline Hb < 7g/dl (p=0.02) and MCV > 80 (p=0.04). MRI/MRA was performed in 31/43 patients and showed ischemic lesions in 5 of them at the mean (SD) age of 7.1 y (1.8) (range 4.5–8.9): no significant difference was observed in the occurrence of lesions between the 2 groups. Conclusions This study confirms the importance of age as predictive factor of conditional to abnormal TCD conversion with a risk of 64% when first conditional TCD occured before the age of 3 years. TCD has to be frequently controled during the 5 first years of life.