A crossable interseptal occluder device comprising: - a support structure; wherein - said support structure comprises a central support structure portion which delimits a lumen; - said support structure comprises a first anchoring portion and an opposite second anchoring portion; - said support structure being configured to expand and contract between a compressed tubular configuration for the insertion through the patient's vasculature, and an expanded configuration, in which the first and second anchoring portions (5, 6) extend radially towards the outside from said central support structure portion to compress a partition therebetween arranging said support structure astride said partition through a defect or hole or opening present in the partition; and wherein - said crossable interseptal occluder device further comprises at least one diaphragm; - said diaphragm being supported by said support structure and arranged to occlude the majority of said lumen when said diaphragm is in a relaxed configuration; - said diaphragm being configured to allow a medical instrument inserted into a first compartment (9 or 10) delimited by said partition to pass through the diaphragm and then through said lumen entering a second compartment (10 or 9) delimited by said partition; wherein - said diaphragm comprises a plurality of occluding bridges; - each of said plurality of occluding bridges comprises an elongated body having opposite elongated body ends (51, 52), and opposite longitudinal edges; - at least a portion of said longitudinal edges of any occluding bridge and at least a portion of said longitudinal edge of a further occluding bridge delimiting at least a slit or a cut into said diaphragm; wherein - both said opposite ends (51, 52) of each occluding bridge are directly or indirectly connected to or supported by said support structure; wherein when under relaxed conditions, said diaphragm is planar in shape and said occluding bridges are tensioned on said support structure; - in a relaxed configuration of said diaphragm, each occluding bridge of said plurality of occluding bridges is disposed close to at least said further occluding bridge of said plurality of occluding bridges; and wherein said diaphragm is an elastic membrane; and wherein said occluding bridges are configured to move away and extend to allow said medical instrument to pass through the diaphragm. - a support structure; wherein - said support structure comprises a central support structure portion which delimits a lumen; - said support structure comprises a first anchoring portion and an opposite second anchoring portion; - said support structure being configured to expand and contract between a compressed tubular configuration for the insertion through the patient's vasculature, and an expanded configuration, in which the first and second anchoring portions (5, 6) extend radially towards the outside from said central support structure portion to compress a partition therebetween arranging said support structure astride said partition through a defect or hole or opening present in the partition; and wherein - said crossable interseptal occluder device further comprises at least one diaphragm; - said diaphragm being supported by said support structure and arranged to occlude the majority of said lumen when said diaphragm is in a relaxed configuration; - said diaphragm being configured to allow a medical instrument inserted into a first compartment (9 or 10) delimited by said partition to pass through the diaphragm and then through said lumen entering a second compartment (10 or 9) delimited by said partition; wherein - said diaphragm comprises a plurality of occluding bridges; - each of said plurality of occluding bridges comprises an elongated body having opposite elongated body ends (51, 52), and opposite longitudinal edges; - at least a portion of said longitudinal edges of any occluding bridge and at least a portion of said longitudinal edge of a further occluding bridge delimiting at least a slit or a cut into said diaphragm; wherein - both said opposite ends (51, 52) of each occluding bridge are directly or indirectly connected to or supported by said support structure; wherein when under relaxed conditions, said diaphragm is planar in shape and said occluding bridges are tensioned on said support structure; - in a relaxed configuration of said diaphragm, each occluding bridge of said plurality of occluding bridges is disposed close to at least said further occluding bridge of said plurality of occluding bridges; and wherein said diaphragm is an elastic membrane; and wherein said occluding bridges are configured to move away and extend to allow said medical instrument to pass through the diaphragm.