A cable for connecting a cardiac pacemaker to an electrode inserted in the heart through the blood stream utilizes a die-clad conductor or a number ofthem, especially several die-clad strands forming a twisted conductor of the stranded type, enclosed in a covering tube of a synthetic elastomer. The core of each die-clad strand is of a highly conducting metal, such as copper or a high-copper alloy. The outer cladding is a metal selected from the group consisting of tantalum, titanium, zirconium, niobium, titanium-base alloys, platinum, platinum-iridium alloys, platinum-palladium alloys and platinum-rhodium alloys. The cladding thickness is in the range from 0.0025 to 0.035 mm, while the cord diameter is between 0.04 to 0.3 mm. When tantalum, titanium, zirconium, niobium or titanium-alloy cladding is used, the outer surface can be made electrically insulating, preferably by anodizing.