An occluder device (20) for occluding a cardiovascular defect or a gap between a medical device and adjacent body tissue comprises: - a compliant balloon (5) defining a fluid-tight balloon chamber and provided with a balloon channel (7) forming a longitudinal passage from a proximal side (B2) to a distal side (Bl) of the balloon； - a tip element (10) disposed at the distal side of the balloon, a base element (4) disposed at the proximal side of the balloon, and connecting means comprising at least one connecting strut (9) attached to the tip element and to the base element, the tip element and the base element each having a guide opening (105a, 105b) substantially coaxial to the balloon channel (7) for slidingly receiving therein a guidewire (106) for the device； - elongated actuating means disposed longitudinally slidable in the balloon channel (7), releasably connectable to the tip element (10), and longitudinally slidable with respect to the base element (4)； - locking means (2, 13) for maintaining a predetermined distance between the tip element (10) and the base element (4)； - proximal connector means (1) for releasably connecting the occluder device (20) to correspondingly configured distal connector means of a catheter device (107)； - the balloon (5) comprising a fluid port (19) for filling and unfilling a fluid into and from the balloon chamber. An occluder system comprises an occluder device (20) and a catheter device (107) cooperating therewith.
