Heart Failure is Accompanied by Loss of Brain Axons Between Short-Term Memory Areas

BACKGROUND: Heart failure (HF) patients have a 4-fold risk of short-term memory impairment which is linked to decreased survival and quality of life. The hippocampus and mammillary bodies are brain structures controlling short-term memory which prior studies suggest are damaged in HF. However, the integrity of interactions between these structures is unknown. Fornix fibers, which connect the hippocampus and mammillary bodies and are essential for survival of cells within the mammillary bodies, are important to maintain memory function . The aim of this study was to compare fornix fiber integrity in HF and healthy subjects. METHODS: Using diffusion tensor imaging (DTI, 4 series) performed with a 3.0 Tesla magnetic resonance imaging scanner, we examined 5 HF (age 53.1±8.2 yrs; LVEF 28.8±6.5) and 10 controls (age 47.5±10.9 yrs). Whole-brain fiber tracks were calculated, and left and right fornix fiber characteristics, including fornix volume, were examined. Fornix fiber characteristics were assessed between groups using ANCOVA, with age as a covariate. RESULTS: There were no significant differences in age, gender, body mass index, or right fornix fiber volumes (HF=0.460±0.02 ml; controls=0.51±0.12 ml; p=0.85) between groups. Left fornix fiber volumes were significantly reduced in HF compared to controls, (0.461±0.15 ml vs 0.855±0.12 ml, p=0.05; Figure). CONCUSIONS: In patients with HF, there is evidence of left fornix fiber volume loss. The processes underlying this left fornix fiber volume loss in HF requires further study, but may include perfusion deficits, sleep-disordered breathing/hypoxia, or nutritional deficiencies. As structural brain damage is present in areas associated with short-term memory deficits in HF, alleviation of HF symptoms alone is unlikely to fully improve cognition.