Pulse Wave Velocity Comparing Estimated and Direct Measures of Path Length in Older Women

Background Carotid-femoral Pulse Wave Velocity (cfPWV) is the gold-standard measure of arterial stiffness. Accuracy of non-invasive cfPWV as meters per second is impeded by surface estimates of aortic length. Our aim was to compare cfPWV measured using distance estimated from surface measurements with distance traced along the length of the aorta using Magnetic Resonance Imaging (MRI) in a cohort of older women. Methods Seventy-four women were recruited from the TwinsUK cohort. cfPWV was measured using the SphygmoCor system (SphygmoCor-PWV). The path between carotid and femoral sites was estimated from surface measurements between the sternal notch and femoral artery applanation point. Aortic distance was measured with MRI to obtain MRI-PWV. cfPWV was recalculated using MRI obtained distance. Results Mean ± standard deviation SphygmoCor-PWV was 9.9 ± 2.1 m/s and MRI-PWV 7.63 ± 1.97 m/s (mean difference 2.2 ± 1.96 m/s, p < 0.001). Distances were considerably higher using surface measures for the SphygmoCor (55.2 ± 3.0, 95% confidence interval 54.4–55.9 cm) compared with MRI (39.9 ± 3.2, 39.2–40.7 cm) with a mean difference of 15.2 cm (14.3–16.2 cm, p < 0.001). Transit times were also marginally longer with the SphygmoCor. When SphygmoCor-PWV was Recalculated using MRI-obtained aortic distance (rec-PWV), the difference between SphygmoCor-PWV and rec-PWV reduced to 0.5 m/s (7.13 ± 1.46 vs. 7.63 ± 1.97 m/s, p = 0.08). Conclusion In these older women, the PWV difference between SphygmoCor and MRI is substantial but reduced when using MRI length estimates. Important differences between PWV measured by Sphygmocor and MRI are mainly due to accuracy of distance measurements, which may need re-addressing in guidelines.