Medical device and method for forming shunt

An expansion body configured to be expandable and contractible in a radial direction, the expansion body comprising:

• a distal end part including a force receiving portion;
• a first expansion portion including a distal-side expansion portion extending radially outward from the force receiving portion toward a direction of the proximal end and a distal-side top portion disposed on a proximal side of the distal-side expansion portion and convexly curved radially outward;
• a second expansion portion including a proximal-side expansion portion extending radially outward from the distal end part of the shaft portion toward a direction of the distal end and a proximal-side top portion disposed on a distal side of the proximal-side expansion portion and convexly curved radially outward;
• a recess that is recessed radially inward, extends to couple the proximal-side top portion with the distal-side top portion, and configured to define a reception space configured to receive a biological tissue when the expansion body is expanded;
• the recess includes a bottom portion located on an innermost side in the radial direction, a distal-side upright portion extending radially outward from a distal end of the bottom portion to the distal-side top portion, and a proximal-side upright portion extending radially outward from a proximal end of the bottom portion to the proximal-side top portion;
• one of the distal-side upright portion or the proximal-side upright portion includes a plurality of energy transfer element arrangement portions on which the plurality of individual energy transfer elements is disposed at a substantially regular interval in a circumferential direction of the expansion body;
• another one of the distal-side upright portion or the proximal-side upright portion includes a plurality of facing portions facing the plurality of individual energy transfer elements when the expansion body is expanded;
• and
• a buffer portion that is disposed in the first expansion portion and is configured to relax a compressive force by deforming in a direction different from a direction from the force receiving portion toward the distal-side top portion along the distal-side expansion portion, or a buffer portion that is disposed in the second expansion portion and is configured to relax the compressive force by deforming in a direction different from a direction from the proximal end of the expansion body toward the proximal-side top portion along the proximal-side expansion portion.

A method for forming a shunt according to the present disclosure forms, in an oval fossa, a shunt through which a right atrium communicates with a left atrium using a medical device including an expansion body that includes a distal end part including a force receiving portion, the expansion body being expandable and contractible in a radial direction, an elongated shaft portion including a distal end part to which a proximal end of the expansion body is fixed, a plurality of energy transfer elements disposed along the expansion body, and a pulling shaft that is disposed inside the shaft portion, connectable to the force receiving portion of the expansion body by protruding from the distal end part of the shaft portion, and slidable with respect to the shaft portion, in which the expansion body includes a first expansion portion including a distal-side expansion portion extending radially outward from the force receiving portion toward a direction of the proximal end and a distal-side top portion disposed on a proximal side of the distal-side expansion portion and convexly curved radially outward, a second expansion portion including a proximal-side expansion portion extending radially outward from the distal end part of the shaft portion toward a direction of the distal end and a proximal-side top portion disposed on a distal side of the proximal-side expansion portion and convexly curved radially outward, and a recess that is recessed radially inward, extends to couple the proximal-side top portion with the distal-side top portion, and defines a reception space that can receive a biological tissue when the expansion body is expanded, the recess includes a bottom portion located on an innermost side in the radial direction, a distal-side upright portion extending radially outward from a distal end of the bottom portion to the distal-side top portion, and a proximal-side upright portion extending radially outward from a proximal end of the bottom portion to the proximal-side top portion, one of the distal-side upright portion or the proximal-side upright portion includes a plurality of energy transfer element arrangement portions on which the plurality of individual energy transfer elements is disposed at a substantially regular interval in a circumferential direction of the expansion body, the other one of the distal-side upright portion or the proximal-side upright portion includes a plurality of facing portions facing the plurality of individual energy transfer elements when the expansion body is expanded, the pulling shaft is configured to apply, to the expansion body via the force receiving portion, a compressive force that makes compression along an axial center of the shaft portion such that the plurality of energy transfer element arrangement portions and the plurality of facing portions approach each other by sliding in a direction of the proximal end with respect to the shaft portion, and the expansion body includes a buffer portion that is disposed in the first expansion portion and is configured to relax the compressive force by deforming in a direction different from a direction from the force receiving portion toward the distal-side top portion along the distal-side expansion portion, or a buffer portion that is disposed in the second expansion portion and is configured to relax the compressive force by deforming in a direction different from a direction from the proximal end of the expansion body toward the proximal-side top portion along the proximal-side expansion portion, the method including:

• inserting the medical device from an inferior vena cava into the right atrium;
• inserting the expansion body in a contracted state into a hole formed in the oval fossa;
• expanding the expansion body in the hole to dispose the biological tissue surrounding the hole in the reception space defined by the recess;
• sliding the pulling shaft in the direction of the proximal end with respect to the shaft portion to compress the expansion body such that the distal-side upright portion and the proximal-side upright portion of the recess approach each other;
• bringing the energy transfer elements disposed to face the recess along the distal-side upright portion or the proximal-side upright portion of the recess into contact with the biological tissue while relaxing the compressive force by deforming the buffer portion in a direction different from the direction from the force receiving portion toward the distal-side top portion along the distal-side expansion portion or relaxing the compressive force by deforming the buffer portion disposed in the second expansion portion in a direction different from the direction from the proximal end of the expansion body toward the proximal-side top portion along the proximal-side expansion portion;
• and
• cauterizing the biological tissue disposed in the reception space using the energy transfer elements in contact with the biological tissue to inhibit occlusion due to natural healing of the hole.