Each year, hundreds of thousands of Americans are treated for cardiac arrythmia with implantable devices. Leads (conductors in a multilumin insulator) are threaded through the venous system from the device to the interior of the heart so that electrical impulses can be used to re-synchronize the heart. Beating of the heart and shoulder movement causes large cyclic strain in the lead. Industry and the FDA would like to increase the reliability of the leads to keep them from failing in fatigue or pushing through the heart wall during implantation. A standards committee (AAMI CRMD WG1) made up of industry, the FDA, physicians, and NIST has been working to improve testing standards, and in the course of their work, they have identified needs in the mechanical modeling of the leads. These multi-material devices can best be modeled with finite elements; close interaction with industrial partners would be required.