Key result
Upper limb Flow-Mediated Dilation was significantly higher than lower limb FMD (7.7% vs 4.9%; p=0.002), but this difference was no longer significant when adjusting for baseline diameter.
Why the study?
Assessing regional vascular function is crucial for understanding systemic cardiovascular health, but whether FMD and PLM yield congruent patterns across upper and lower limbs and how sex influences these relationships remained unclear.
Do Flow-Mediated Dilation and Passive Limb Movement yield congruent, interchangeable patterns across the upper and lower limbs in healthy individuals?
Cross-Sectional (n=20)
Do Flow-Mediated Dilation and Passive Limb Movement yield congruent, interchangeable patterns across the upper and lower limbs in healthy individuals?
Answers are grounded in this paper and cite their sources.
Limb-specific endothelial measures should not be assumed interchangeable; leaves open optimal site and technique for systemic vascular assessment.
Assessing regional vascular function is crucial for understanding systemic cardiovascular health. This study primarily investigated whether Flow-Mediated Dilation (FMD) and Passive Limb Movement (PLM) yield congruent, interchangeable patterns across the upper (UL) and lower limbs (LL). Secondarily, we evaluated sex-specific influences on these regional vascular relationships. Twenty healthy individuals (10 males, 10 females) underwent brachial and popliteal FMD, alongside axillary and femoral PLM, in a counterbalanced single session. Baseline diameters, FMD%, allometrically scaled FMD, and blood flow (BF) PLM parameters (peakBF, ΔpeakBF, Area Under the Curve [AUC]) were analyzed. Regarding our primary aim, FMD% was significantly higher in UL than LL (7.7±2.9% vs 4.9±1.8%; p=0.002) and not correlated between limbs (r=0.11, p=0.650). However, when analyzed using an allometric mixed model with baseline diameter as a covariate, this limb difference was no longer significant (p=0.334). PLM ΔpeakBF was lower in UL than LL (ΔUL-LL = -68.3%; p<0.001) but showed significant inter-limb correlations (r=0.50, p=0.024). No limb x sex interaction was found for FMD% (p=0.889) or allometric FMD% (p=0.815). However, a significant limb x sex interaction emerged for PLM AUC (p<0.001), driven by a higher absolute AUC in the LL for males (p<0.001) and a higher volume-normalized AUC in the UL for females (p=0.003). In conclusion, brachial and popliteal FMD are not interchangeable, providing complementary, region-specific information heavily influenced by vessel size, and FMD% is not affected by sex. PLM UL and PLM LL provide partially convergent but not equivalent information, warranting caution when comparing limbs, particularly when sex is a variable of interest.
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Fioraso et al. (2026) conducted a cross-sectional in Healthy (n=20). Upper limb vascular assessment vs. Lower limb vascular assessment was evaluated on Flow-Mediated Dilation (FMD%) (p=0.002). Upper limb Flow-Mediated Dilation was significantly higher than lower limb FMD (7.7% vs 4.9%; p=0.002), but this difference was no longer significant when adjusting for baseline diameter.
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