An active implantable medical device assembly, comprising: - a sub-cutaneous autonomous unit comprising:. a tight body housing electronic circuits and electric supply means of these electronic circuits; and. extending this body, at least one detection and/or therapy delivery lead, this lead comprising at least one detection and/or therapy delivery electrode; and - at least one intracorporeal autonomous leadless capsule (200; 300) adapted to be implanted in or against an organ and comprising:. a tight body (202; 302) housing electronic circuits and electric supply means of these electronic circuits;. means (204; 304) for the anchoring to a wall of said organ; and. at least one detection and/or therapy delivery electrode (204; 304) adapted to come into direct contact with said organ, wherein the autonomous unit and the leadless capsule (200; 300) each comprise emitter/receiver means (118a; 208; 308) for mutual intracorporeal wireless communication, the autonomous unit operating as a master and the leadless capsule(s) operating as slaves under the control of the master autonomous unit, and wherein the autonomous unit further comprises:. means for centralizing the data transmitted by the leadless capsules, and. means (118b, 112) for communication with the outside, adapted to operate a remote-transmission, towards a remote equipment, of the data collected by the data centralization means, the assembly being characterized in that: - said at least one detection and/or therapy delivery lead is a microlead comprising at least one microcable formed of an electrically conductive core cable connected to a pole of said electronic circuits, with an insulation layer surrounding the core cable and comprising at least one selectively-naked zone formed in the insulation layer and intended to form said detection and/or therapy delivery electrode, the diameter of the microlead being of at most 1 French (0.33 mm) in its most distal region comprising said selectively-naked zone; and - said autonomous unit is a hybrid capsule whose volume is of at most 1 cm 3 and in which:. the hybrid capsule is devoid of electric connector between the microlead and the electronic circuits,. the at least one microlead extends said body on one side of the latter, and. the core cable of the microcable, or of each microcable, is directly connected to a respective pole of the electric circuits of the hybrid capsule. - a sub-cutaneous autonomous unit comprising:. a tight body housing electronic circuits and electric supply means of these electronic circuits; and. extending this body, at least one detection and/or therapy delivery lead, this lead comprising at least one detection and/or therapy delivery electrode; and. a tight body housing electronic circuits and electric supply means of these electronic circuits; and. extending this body, at least one detection and/or therapy delivery lead, this lead comprising at least one detection and/or therapy delivery electrode; and - at least one intracorporeal autonomous leadless capsule (200; 300) adapted to be implanted in or against an organ and comprising:. a tight body (202; 302) housing electronic circuits and electric supply means of these electronic circuits;. means (204; 304) for the anchoring to a wall of said organ; and. at least one detection and/or therapy delivery electrode (204; 304) adapted to come into direct contact with said organ,. a tight body (202; 302) housing electronic circuits and electric supply means of these electronic circuits;. means (204; 304) for the anchoring to a wall of said organ; and. at least one detection and/or therapy delivery electrode (204; 304) adapted to come into direct contact with said organ,. means for centralizing the data transmitted by the leadless capsules, and. means (118b, 112) for communication with the outside, adapted to operate a remote-transmission, towards a remote equipment, of the data collected by the data centralization means, - said at least one detection and/or therapy delivery lead is a microlead comprising at least one microcable formed of an electrically conductive core cable connected to a pole of said electronic circuits, with an insulation layer surrounding the core cable and comprising at least one selectively-naked zone formed in the insulation layer and intended to form said detection and/or therapy delivery electrode, the diameter of the microlead being of at most 1 French (0.33 mm) in its most distal region comprising said selectively-naked zone; and - said autonomous unit is a hybrid capsule whose volume is of at most 1 cm 3 and in which:. the hybrid capsule is devoid of electric connector between the microlead and the electronic circuits,. the at least one microlead extends said body on one side of the latter, and. the core cable of the microcable, or of each microcable, is directly connected to a respective pole of the electric circuits of the hybrid capsule.. the hybrid capsule is devoid of electric connector between the microlead and the electronic circuits,. the at least one microlead extends said body on one side of the latter, and. the core cable of the microcable, or of each microcable, is directly connected to a respective pole of the electric circuits of the hybrid capsule.