A compact implantable medical assembly is comprised of a medical device connected to an electrochemical cell. The medical device is comprised of a housing enclosing at least one electrical circuit and including an end having a perimeter edge and a contact opening therethrough. The electrochemical cell is comprised of a casing having a sidewall extending to a distal end and a proximal end forming a proximal opening. The proximal casing end is joined to the medical device housing. A glass-to-metal seal supports a terminal pin extending from within the casing through the proximal casing opening and through the contact opening in the end of the housing. The terminal pin is connected to the electrical circuit contained within the housing. That way the cell serves as the power source for the medical device with both the cell and medical device being exposed to body fluid.