Dynamic Vascular Analysis Shows a Hyperemic Flow Pattern in Sickle Cell Disease

Abstract

By the age of 20 years, 10% of sickle cell disease (SCD) patients have experienced a stroke. It is unclear if SCD stroke is due primarily to hemodynamic effects of intracranial stenosis, or metabolic failure from anemia. Transcranial Doppler ultrasound (TCD) identifies a SCD subgroup with high stroke risk, but high mean flow velocity (MFV) can be due to stenosis or high flow rate, as with metabolic hyperemia of severe anemia. Dynamic Vascular Analysis (DVA; New Health Sciences, Inc., Bethesda, MD) is a new way to analyze TCD data, with potential to separate structural from metabolic causes of high MFV. Eighty SCD patients, regardless of hemoglobin genotypes, aged 2 to 22 years, without clinical stroke or transient ischemic attack (TIA), who had TCD (1/1/02 to 1/1/04) as part of routine outpatient clinical follow-up, with both the TCD report and study videotape available, were included. Waveforms were reviewed and marked by protocol, and DVA indices calculated including MFV, pulsatility index (PI), systolic acceleration (SA), dynamic flow index (DFI), dynamic pressure index (DPI), and dynamic compliance index (DCI). Mean and standard deviation were defined for the whole group, and for four subgroups, by age. MFV, DFI, and DPI were highest at 6- to 9-year-olds, declining thereafter. The 14- to 22-year-old group was also compared to a group of healthy young athletes (15- to 22 years old). SCD patients had higher MFV, lnSA, DFI, DPI, and lower PI and DCI in most segments, suggesting global hyperemia. This is the first report of cross-sectional results of DVA in a cohort of SCD outpatients without prior clinical stroke (TIA). These results suggest hyperemia without significant focal intracranial stenosis. There were also differences between asymptomatic SCD and young athletes, and the MFV, DFI, and DPI were highest at the age of 6 to 9 years, decreasing as age increased.