A schematic of the hypothesized physiological mechanism for reduced capillary oxygen offloading secondary to accelerated arteriovenous transit. (A) Under healthy conditions, normal arteriovenous transit allows for sufficient oxygen offloading in the capillaries. (B) Under altered hyperemic conditions such as in chronic anemia, compensatory accelerated CBF may shorten the red cell residency time within the capillaries, due to rapid arteriovenous transit, thus resulting in reduced oxygen offloading and OEF. (C) Representative examples of a participant from each VHS on ASL perfusion-weighted imaging. For VHS of 0, no hyperintensity is observed in the superior sagittal sinus nor straight sinus. For VHS of 1, a region of focal hyperintensity (orange arrow) is observed in the superior sagittal sinus but does not persist spatially to the level of the torcula. For VHS of 2, diffuse hyperintensity (orange arrows) is observed along the superior sagittal sinus across multiple axial slices and extends to the torcula. SaO2, arterial oxygen saturation; SvO2, venous oxygen saturation.
