A sensing/pacing lead including a microcable having a diameter of at most 2 French (0.66 mm). The microcable includes an electrically conductive core cable including a plurality of strands and a composite structure formed from at least a structuring material and a radiopaque material, the radiopaque material constituting at least about 0.008 mm2 of the core cable cross section. The plurality of strands of the core cable comprises a first set of individual strands formed from the structuring material and a second set of individual strands formed from the radiopaque material, or a plurality of strands each comprising a first and second layer, one of which is the structuring material and the other the radiopaque material. The microcable further includes a polymer insulation layer at least partially surrounding the core cable and at least one electrode.