The device comprises a sealed body housing electronic circuits, and extending from said body, a microlead comprising microcables connected to remote electrodes. The device has no connector between the microlead and the electronic circuits. Each microcable is permanently connected to its pole by connection means. The connection means comprises an insulating base hermetically crossed by feedthrough pins, a support for the base, conductive connection parts each comprising a first passage for a microcable and a second passage for a feedthrough pin, an insulating guiding and holding part mounted on the support and locked thereon. The guiding and holding part having cavities for the connection parts, each cavity opening in its bottom on a passage wherein a pin projects. The device also includes a transition and protection element encapsulating the guiding and holding part, the connection parts and the adjoining regions of the microcables.