Reliability of the Passive Leg Movement Assessment of Vascular Function

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PURPOSE: Although vascular function is an independent predictor of cardiovascular disease risk, and therefore has significant prognostic value, there is currently not a single clinically accepted assessment of vascular function. The recently emerged passive leg movement (PLM) assessment of vascular function appears to reflect predominantly endothelium-dependent vasodilation and can identify changes in vascular health with both advancing age and pathology. However, the reproducibility of the PLM model has yet to be examined. METHODS: Seventeen healthy subjects (age: 24 - 37 yr) were studied on three separate experimental days, allowing five total trials of PLM to be performed on each subject, three within day (Trials 1-3) and three between day (Trials 1,4,5). The leg blood flow (LBF) response to PLM was assessed with Doppler ultrasound, and expressed as the change from baseline to peak (ΔLBFpeak). RESULTS: The PLM-induced ΔLBFpeak was similar across all five trials (Trial 1: 1,030 ± 113, Trial 2: 960 ± 107, Trial 3: 909 ± 106, Trial 4: 1,000 ± 139, Trial 5: 973 ± 135 ml/min; p = 0.27) and these ΔLBFpeak values were significantly correlated both within (r: 0.64 - 0.88; p < 0.001) and between days (r: 0.73 - 0.85; p < 0.001). Also these repeated PLM assessments revealed high intraclass correlation coefficients (ICC) (within-day: 0.91; between-day: 0.93). Finally, despite the inclusion of all data, although some were clearly statistical outliers, PLM measurements exhibited a coefficient of variation of ~20%. CONCLUSIONS: The blood flow response to PLM is both consistent and reproducible between trials, whether performed repeatedly on the same day or on separate days. In combination with the growing evidence that PLM can distinguish between healthy individuals and populations with known vascular dysfunction (elderly, heart failure, sepsis, COPD, etc.), these findings support the continued movement to foster clinical acceptance of PLM as an effective assessment of vascular function and future cardiovascular disease risk.