Barouh Berkovits at American Optical Co of Boston, MA designed the first “Demand Pacemaker” – what we now know as a VVI pacemaker. As other companies in the 1970s, American Optical developed a nuclear-battery-powered version of their pacemaker.
American Optical used a 3Ci Pu-238 Radioisotope Thermal Generator (RTG) produced by Fred Hittman’s Hittman Nuclear Development Corp. (Model NB-200). It consisted of a tiny 8 Ci slug of metallic Plutonium 238 (Pu-238). The radiation produced by the Pu-238 bombarded the walls of its container, producing heat that a thermopile then converted to an electrical current. A thermopile is a stack of thermocouples, which are devices that convert thermal energy directly into electrical energy using Seebeck effect. The thermocouple was made of two kinds of metal (or semiconductors) connected to each other in a closed loop. If the two junctions are at different temperatures, an electric current will flow in the loop. Continue reading
CCC is one of the oldest pacemaker manufacturers in the world. It was founded in 1969 by Dr. Orestes Fiandra, who performed the first succesful, human, long-term pacemaker implant in the world.
Intrapace was founded in Mountain View, CA by 
Transneuronix, Inc. was founded in 1995 and was based in Mount Arlington, New Jersey. It was acquired by Medtronic in 2005.
Transoma was the name that Data Sciences International of St Paul, MN adopted in 2003 when it re-fucused its animal telemetry implant business to develop an implantable wireless system to capture electrocardiogram data for diagnosing human cardiac arrhythmias, as well as to monitor the electrical activity of the heart and transmit data from the patient’s home to monitoring centers.