Impact of Aging, Sex, and Hypertension on Aortoiliac Hemodynamics: A 4-Dimensional Flow Magnetic Resonance Imaging Study.

BACKGROUND: The impact of aging, sex, and hypertension on the aortoiliac arterial system is poorly characterized. This study aimed to comprehensively evaluate iliac artery hemodynamics and the vascular aging phenotype using 4-dimensional flow magnetic resonance imaging. METHODS: In this cross-sectional study, 235 participants (aged 18-97 years) without major vascular disease underwent 4-dimensional flow magnetic resonance imaging. The structural (area), basic hemodynamic (velocity, flow, resistive/pulsatility indices), and wall shear stress (WSS) parameters of the infrarenal aorta and left and right common arteries were quantified. Statistical analyses included group comparisons, correlation, multiple linear regression, effect size evaluation, and propensity score matching for hypertension. Multiple comparison corrections were performed throughout this study as appropriate. RESULTS: Vessel area increased with aging and was higher in men. Systolic velocity decreased with age but showed no significant sexual dimorphism. A distinct aging pattern emerged for WSS: time-averaged (TA) axial WSS significantly decreased with age (P<0.001), whereas TA circumferential WSS and oscillatory shear index increased (P<0.001). Multiple linear regression confirmed that age (P<0.001) and antihypertensive medication (P<0.01) were associated with lower TAWSS, whereas hypertension was associated with higher TAWSS (P<0.01). Regarding OSI, higher OSI was associated with higher age (P<0.001) and male (P<0.001). After propensity score matching, analysis revealed no statistically significant difference of hemodynamics parameters in participants with or without hypertension. CONCLUSIONS: This study delineates an aortoiliac aging phenotype characterized by decreasing TA/axial WSS and increasing circumferential WSS/OSI. The role of hypertension in vascular remodeling needs further validation in larger cohorts.