Non-invasive vascular function tests: their pathophysiological background and clinical application.

The arterial wall has 3 layers (ie, the intima, including the endothelium, the media, and the adventitia); each of these layers has individual roles in systemic circulation. The vascular endothelium regulates the vascular tone, hemostasis and/or vascular permeability, and the media is the major determinant of arterial elasticity, which regulates the conduit function (delivery of blood to tissues) and cushioning effect (for generation of continuous blood flow). Failure of these functions results in organ/vascular damage. Several non-invasive methods are currently used to assess vascular dysfunction, including measurement of flow-mediated vasodilatation of the brachial artery induced by reactive hyperemia (FMD), pulse wave velocity (PWV), the augmentation index (AI), and central blood pressure. Endothelial dysfunction, which is assessed by FMD, contributes to the initiation/progression of atherosclerosis. Increased arterial stiffness, which is assessed by the PWV and/or AI, causes increased cardiac afterload, impaired coronary arterial blood supply, atherogenesis and/or microvascular damage. The combination of risk stratification by assessment of conventional risk factors for cardiovascular disease (CVD) with not only a morphological assessment of vascular damage, such as carotid ultrasound examination, but also vascular function tests, may be a useful strategy for the management of CVD and its related risk factors. (Circ J 2010; 74: 24 - 33).