Axial and Radial Diffusivity Measures Detect Brain Tissue Injury in Heart Failure Patients

Heart failure (HF) patients show brain tissue loss or injury in autonomic, cognitive, and emotional regulatory areas (1, 2); the regions with tissue injury overlap sites of altered functional MRI signals to autonomic challenges (3, 4). Some structural injury appears on T2-relaxometry procedures, and could result from different pathological processes, including hypoxia/ischemia accompanying perfusion or breathing characteristics in the syndrome. These processes could introduce axonal loss or myelin loss, either independently or in combination; however, T2-relaxomety indicates only generalized tissue damage. In contrast, diffusion tensor imaging-based indices, including axial diffusivity, which measures diffusion of water molecules parallel to the tissue fibers and indicates axonal status, and radial diffusivity, which assesses water diffusion perpendicular to the fibers and primarily shows myelin changes (5) can offer additional insights into types of pathology in HF. We aimed to assess axial and radial diffusivity in HF patients to reveal types of axonal tissue injury present in affected brain sites.