An intravascular implantable system for providing electrical stimulation of tissue inside an animal to deal with a clinical condition is described. The system comprises a power supply module supplying energy to the implantable system, an implanted control module controlling operation of the implantable system and producing desired digital waveforms. Each desired digital waveform has an envelope with a predetermined attribute. An implanted intravascular sensing module sensing at least one parameter of interest for the purpose of dealing with the clinical condition. An intravascular stimulation module is provided to electrically stimulate the tissue with an output waveform that is substantially similar to the desired digital waveform produced by the control module.