Introduction:
Human immunodeficiency virus (HIV)-infected individuals are at high risk for ischemic stroke. We measured cerebral blood flow (CBF), oxygen extraction fraction (OEF), and autoregulation in HIV infected subjects and controls.
Methods:
In treatment-naive HIV infected subjects and age-, gender-, and race-matched controls, OEF was measured by using MRI T2*-weighted echo-planar imaging sequences and CBF was measured by MRI pulsed arterial spin labeling (PASL) approach. Static cerebral autoregulation was determined by measuring changes in CBF and OEF, in response to ≈10% reductions in MAP induced by using IV Nicardipine infusion. All images were acquired using a Siemens 3T MR scanner (Treo, Siemens Medical Systems Inc). Cerebral autoregulation was measured globally and regionally in gray matter (GM), white matter (WM) and subcortical GM. Autoregulatory Index (AI) was computed using the equation AI = %CBF change/% MAP change supplemented by CBF associated OEF changes. Nominal p-values are uncorrected for multiple comparisons.
Results:
Forty-one treatment naive HIV-infected subjects and 47 age-, gender-, race-matched controls participated. HIV-infected subjects had higher CBF in cortical GM compared to the controls (76.8± 12 mL/100 g/min versus 71.6 ± 11 mL/100 g/min; p= 0.04), but not in white matter (30.9± 8 mL/100 g/min versus 30.0 ± 8 mL/100 g/min; p = 0.60) or subcortical GM (62.8± 13 mL/100 g/min versus 61.3 ± 13 mL/100 g/min; p = 0.57). Whole brain (WB), GM, WM, and subcortical GM, OEF were similar between the groups (p > .05). The median AI were similar between cases and controls in WB (0.40 vs 0.18, p=0.86), GM (0.10 vs. 0.16, p=0.87), WM (0.80 vs. 0.87, p=0.31), and subcortical GM (1.65 vs. 1.77, p=0.26). A 12-month follow-up (N=30) in HIV-subjects on antiretroviral therapy did not produce a significant change in CBF or OEF in the WB, GM, WM, or subcortical GM (Paired sample t test p>0.05). Similarly, no changes were noted on the AI (Wilcoxon Match Rank test p>0.05).
Conclusions:
AI was similar between HIV cases and control and remained so after 12-months of antiretroviral therapy. We found no evidence of a defect in autoregulation to explain the high-risk of ischemic stroke documented in other studies.
Increased Cortical Cerebral Blood Flow in Asymptomatic Human Immunodeficiency Virus-Infected Subjects
