The Need to Consider Pro-Active Treatment for Cerebral Artery Conditional Blood Velocity Determined By Transcranial Doppler Ultrasonography (TCD) in Sickle Cell Disease (SCD)

Introduction Cerebral artery peak systolic blood velocity (PSV) or timed average mean of the maximum blood velocity (TAMMV) determined by TCD in children of age 2-16 years with SCD is normal (NV) if TAMMV <170 cm/sec or PSV <200 cm/sec; abnormal (AV) if TAMMV > 200cm/s or PSV > 250 cm/sec; and conditional (CV) if TAMMV is 170-199cm/sec or PSV 200-249 cm/sec. Internal carotid (ICA) or middle cerebral (MCA) artery AV is associated with a stroke risk of 10% /year, CV a risk of 3-4% /year [Adams et al. Long-Term stroke risk in children with SCD screened with TCD. Ann Neurol 1997; 42: 699–704]. Blood transfusion or hydroxycarbamide is used to treat AV, but active treatment is currently not considered the standard of care for conditional velocity, although it could progress to abnormal values.

Objective To evaluate the need for pro-active treatment of cerebral artery conditional blood velocity in children of age 2-16 years with SCD.

Methods Following IRB approval and informed consent/assent, 308 children with SCD (126 girls and 182 boys, age 2-16 years) had TCD to determine PSV (n=193) or TAMMV (n=115) in the MCA, ICA and anterior cerebral arteries (ACA). This design was to make the research findings relevant to hospitals with TCD equipment that measure either PSV or TAMMV. Exclusion criteria were blood transfusion in the previous 4 months, therapy with hydroxycarbamide, omega-3 fatty acids or other agents that affect the severity of SCD, pregnancy, breast feeding, chronic disorders unrelated to SCD (such as diabetes mellitus) and stroke. Children with AV were started on a blood transfusion program. Those with conditional PSV were randomized in a 2:1 ratio to receive either standard care of SCD and active treatment with omega-3 fatty acids and potassium thiocyanate, or standard care only. After 3 months, measurement of PSV in the ICA, MCA and ACA was repeated. Study data were analysed with the Statistical Package for Social Sciences version 23 (IBM, USA).

Results In the TAMMV cohort of 115 children, 96 (84%) had NV, 7 (6%) AV, and 12 (10%) CV. Figure 1 shows the cumulative frequency of TAMMV in the MCA where most AV and CV occurred. In the PSV cohort of 193 children, 150 (77.7%) had NV, 7 (3.6%) AV, and 36 (18.7%) CV. There were no significant differences in gender or age distribution between the PSV and TAMMV cohorts. Altogether, cerebral artery blood velocity was normal in 246/308 children (80%), abnormal in 14 (4.5%) and conditional in 48 (15.5%). The PSV in 21 patients randomized to active treatment of conditional blood velocity or standard SCD care are shown in Table 1. After 3 months, PSV reduced to normal (<200cm/sec) in a significantly higher proportion (11/14 or 79%) of children on active treatment compared with 3/7 (43%) on standard care only, p = 0.04. Change in the right MCA median PSV showed a significant difference of 54cm/sec between children on active treatment who had a reduction from 201.5 cm/sec to 169.5 cm/s, and the standard care group with a rise from 184cm/s to 206 cm/sec (p = 0.018). One of 7 patients on standard care (14%) but none of 14 on active treatment (0%) had progression of PSV from conditional to abnormal. Reduction in conditional velocity following active treatment has been reported from other studies [Lagunju et al, Pediatr Blood Cancer 2015;62:1587–91; Estepp et al. Br J Haematol 2021;194:463–8]. Although not statistically significant, pre/post-treatment median steady state Hb level in actively treated patients showed an upward trend [6.8/7.3g/dl]; and the median platelet count a downward trend: 278/235 x10⁹/l. The standard care group had opposite, but also not significant, trends: 7.45/7.0 g/dl, 224/261 x10⁹/l.

Discussion and Conclusion The 15.5% prevalence of conditional velocity translates to 15,500 /100,000 children born annually with SCD in our country, or 46,500 worldwide, of whom 1,860 (4%) may have stroke. If 14% of CV progress to AV, that is 6,510/year globally. If all are not treated, a reality in resource-limited places, any number up to 651 (10%) may develop stroke. The annual incidence, cumulative prevalence and progression rates of CV, and the significant difference in the proportion that revert to NV on active treatment compared to standard care only, suggest that there is need to consider CV for active treatment. This will prevent the cumulation of more than 1,860 children who develop stroke every year with its health, psychosocial and economic burden to the patients, their families and society.