Abstract
The flow-mediated dilation (FMD) test is a method of evaluating the vascular endothelial function and has been popular as it is noninvasive and readily performed by a skillful ultrasound technician. The FMD test, however, evaluates only the maximal increase in vascular diameter mediated by the increases in blood flow after the release of the occlusive cuff and does not evaluate the arterial viscoelastic properties. Therefore, this paper proposes a new index, called log-linearlized viscoelasticity, to evaluate the arterial viscoelastic properties using the arterial diameter and blood pressure measured in a beat-to-beat manner during the FMD test. To six healthy people, we performed the FMD test to measure the arterial diameter and blood pressure with ultrasound diagnostic imaging equipment and noninvasive continuous arterial blood pressure monitor. As a result, the maximal vasodilatation ratio of FMD (%FMD) was obtained after cuff occlusion. In comparison with the arterial viscoelastic characteristics before FMD test, the stiffness of the arterial wall β and the viscosity of the artery η temporarily decreased and increased, respectively. The change of log-linearlized viscoelasticity after cuff occlusion may be caused by vascular endothelial function. Vascular endothelial function might thus be estimated using the arterial viscoelasticity β and η.
