An implantable medical lead for implantation in a patient which has at least one electrical conductor connected to at least one electrode and/or sensor of said lead. The at least one conductor is arranged within a continuous sheet of a polymer material. A distal portion of the lead is adapted to be located in or at a heart of said patient and a proximal portion of said lead is connectable to an implantable medical device and arranged such that, when connected to the device, at least a part of the proximal portion of the sheet is placed in close proximity to said medical device. At least the proximal portion of the polymer sheet material is processed in at least a first heat process stage such that an inherent resistance to wear of the polymer sheet material is substantially maintained, and the distal portion of said polymer sheet material is processed in at least a second heat process stage in which a polymer morphology of said polymer material is altered such that an inherent flexibility of the polymer sheet material is substantially increased.
