The invention relates to medical devices such as pacemakers, pulse generators, cardioverter-defibrillators and the like and more particularly relates to modular and reconfigurable medical system platforms and methods of designing, testing, controlling and implementing diverse therapies, diagnostics, physiologic sensors and related instrumentation using said medical system platforms. Methods, systems and devices provide a new design platform for implantable and external medical devices such as pacemakers, defibrillators, neurostimulators, heart monitors, etc. A real-time, highly flexible system of software and hardware modules enables both prototypes and products to respond to patient and customer needs with greater design and manufacturing efficiency. Certain embodiments integrate a general-purpose processor with interface circuitry to provide a standard platform for implementing new and conventional therapies with software models rather than custom circuitry. The platform described may be used as a simulation environment, development and test platform and/or may be used as architecture for building new medical devices.