[What is a microcirculatory disorder in chronic degenerative vascular disease? (author's transl)].

At present, it is generally accepted that "microcirculatory disorders" are important, sometimes decisive complications of degenerative vascular diseases. In an attempt to sharpen the profile of these sometimes vaguely defined abnormalities, new definitions of "microcirculatory disorders" are proposed. After describing the normal circulation on the basis of the normal vascular integrity, the normal composition of blood and interstitial fluid, the normal rheological behavior of blood cells (in their natural habitat, the flowing blood) and the normal vascular tone, it becomes possible to define abnormalities. These abnormalities are not only quantitatively (as hypoperfusion) but also qualitatively different from the normal state of microcirculation. A microcirculatory disorder is therefore defined as a consequence of autonomous and autochthonous abnormalities of vascular wall, blood, and interstitial cells and fluids, which are basically independent of the macrocirculatory abnormalities but highly effective in complicating them. Proposals for therapeutic consequences of such concepts are given and criteria for the classification of drugs effective in the microcirculation are delineated. Lastly, in vitro and in vivo tests allowing to classify the success of the therapy are proposed. In the complex, chronic and multifacetted obliterative vascular diseases a pharmacological goal short of "clinical efficacy" is defined: a "useful therapeutic effect".