Abstract: An endocardiac lead of the type including a conductive spiral winding 2 placed inside a sheath 1 made of a flexible material being insensitive to body fluids. This spiral winding 2 is electrically connected to an electrode 3 intended for being brought into contact with the inner wall of the heart. The electrode 3 is hollow and accommodates along its centerline a deformable helix 6 intended for fastening the lead into the heart muscle. The inner diameter of the electrode 3 is smaller than the outer diameter of the undeformed helix 6. The helix 6 presents a sufficient longitudinal elasticity modulus for being retractable inside the electrode 3 with a mechanical deformation, while the helix will substantially recover its initial shape during its extraction out of the electrode and secure the electrode to the tissue. The helix 6 may be made of a nickel-titanium based alloy.