One of the main subdivisions included in the Updated version of the classification for vascular malformations. It is differentiated from slow-flow lesions and developmental anomalies of named vessels lesions. Fast-flow vascular malformations can be subdivided into isolated, multifocal and syndromic lesions. The main change was to use flow velocity as a determinant between lesions with arterial components (fast- flow) and lesions with slow-flow components such as venous, lymphatic and capillary.