This paper describes the development by ELA Medical of an analog library dedicated to implantable pacemakers and defibrillators using the VHDL-AMS language for mixed-signal ASICs. ELA Medical has been a leading company since 1977 for medical devices used in the diagnosis and treatment of heart rhythm disorders. The objective is to provide designers with a ready-to-use customized library for mixed-signal top-down and bottom-up methodologies. The dramatic gain in simulation speed by using behavioral models allows more exhaustive functional validation within an acceptable simulation time. The ADMS mixed-signal simulator from Mentor Graphics has been used with design kit environments provided by major silicon vendors.