IEC 60601-2-31:2008 applies to the basic safety and essential performance of external pacemakers powered by an internal electrical power source. The minimum safety requirements specified in this particular standard are considered to provide for a practical degree of safety in the operation of external cardiac pacemakers with an internal power source. This particular standard amends and supplements IEC 60601-1 (third edition, 2005): Medical electrical equipment - Part 1: General requirements for basic safety and essential performance. This second edition cancels and replaces the first edition published in 1994 and its Amendment 1 (1998). This second edition of IEC 60601-2-31 is aligned with IEC 60601-1:2005, and contains minimal technical revisions from the first edition.