Abstract Body (Do not enter title and authors here): Background Cardiovascular (CV) risk factors such as hypertension have been linked to accelerated cognitive decline with aging but underlying hemodynamic mechanisms are unclear. Aortic stiffening, quantified by pulse wave velocity (PWV), may contribute to microvascular injury by elevating transmitted pulsatility and triggering vascular adaptations that limit blood flow. Using a novel single-session 4D flow MRI protocol we assessed heart-brain hemodynamics in cognitively asymptomatic adults with and without hypertension.
Hypotheses Age, higher CV disease (CVD) risk, and aortic PWV are associated with amplified intracranial pulsatility and reduced flow/velocity.
Methods Data have been collected in 24 cognitively asymptomatic adults (62.3±7.4 years; 7 males; 8 hypertensive; Telephone-MoCA≥17). CVD risk was determined using the simplified Framingham model, and physical activity was assessed by self-report. CV and intracranial 4D flow research sequences were acquired at 3T (Prisma, Siemens). Preprocessing and segmentation of aorta and Circle of Willis (CoW) were applied. Mean and peak velocity (Vmean, Vmax; m/s), and time-to-peak (TTP; ms) were quantified voxel-wise. Flow (ml/s), pulsatility index (PI), and aortic PWV were quantified as detailed in Fig 1. PWV was inverse transformed (PWV.T; ms/m).
Results Hypertensive participants were older (69.1±7.4 vs 58.9±4.5 years, p<0.01), had higher CoW PI (1.16±0.28 vs 0.99±0.09, p=0.04), and lower CoW Vmax (0.71±0.06 vs 0.79±0.09 m/s, p=0.03) than controls. CVD risk score was associated with higher PI and lower velocities in the CoW (Fig 2). Higher physical activity was associated with higher CoW Vmean, Vmax, and flow (rho=0.47-0.48; p=0.02-0.03) and lower PI (rho=-0.43, p=0.04). Inverse relationships were found for: CoW Vmax with aortic PWV.T (r=-0.46, p=0.03), and CoW PI with TTP in both regions (r_aorta=-0.43, p=0.04; r_CoW=-0.45; p=0.03). CoW and aortic TTP showed moderate correlation (r=0.41, p=0.04; Fig 3).
Conclusion Preliminary results show correlations between heart and brain hemodynamic measures. Hypertension and CVD risk were related to adverse CoW hemodynamics, while physical activity showed favorable associations. Aortic PWV was related to lower intracranial peak velocity, suggesting a possible downstream effect. Expected association between aortic PWV and CoW PI was not observed. Findings highlight the complexity of heart-brain hemodynamics and support ongoing recruitment for stratified age-matched analysis.