A support layer for a synthetic root comprises at least a first region and a second region. The pattern, material, density and/or tension of the support layer in the first region is different to that in the second region. The support may be formed from a knitted, woven, braided or 3D-printed material. The support layer may be comprised within a synthetic aortic or pulmonary root. In at least one region the synthetic root may have a multi-layered structure with the support layer disposed between an inner and an outer nanofiber layer.
