A lead assembly adapted for endocardial fixation to a human heart is provided. The lead assembly includes a lead body that has a proximal end provided with a connector for electrical connection to a cardiac stimulator. The cardiac stimulator may be a pacemaker, a cardioverter/defibrillator, or a sensing instrument. The distal end of the lead body is connected to a tubular electrode housing. The lead body consists of one or more noncoiled conductor cables surrounded by a coextensive insulating sleeve. Each conductor cable consists of a conducting element covered by a coextensive insulating sleeve. The conducting element may be a single filament wire or a plurality of individual conductor wires. In contrast to conventional leads, the lead body of the present invention does not require coiled conductor wires. Lead body diameters of 1.04 mm or smaller are possible.