Medical device and method for forming communication hole

A method for forming a communication hole that allows communication between a right atrium and a left atrium in an atrial septum using an expansion body that is expandable and contractible in a radial direction, the method comprising:

• inserting an expansion body, the expansion body including a recess that is recessed radially inward upon expansion of the expansion body and that defines a reception space capable of receiving a biological tissue, into a first through hole formed in the atrial septum to place a tissue surrounding the first through hole in the reception space defined by the recess;
• expanding the recess of the expansion body in the radial direction to expand the first through hole to a second through hole larger than the communication hole;
• cauterizing the tissue surrounding the second through hole with a plurality of electrode units disposed in the recess of the expansion body in such a manner that a cauterization region of the tissue surrounding the communication hole has a length of 3.0 mm or less extending in the radial direction from an edge of the communication hole and a ratio of 40% or more to a circumferential length of the edge of the communication hole in a circumferential direction;
• and
• forming the communication hole by contracting and removing the expansion body from the second communication hole after the cauterization of the tissue surrounding the second through hole.

A medical device for forming a communication hole in a biological tissue, the medical device comprising:

• an expansion body that is expandable and contractible in a radial direction;
• and
• a plurality of electrode units disposed on the expansion body, wherein
• the expansion body has a recess that is recessed radially inward upon expansion of the expansion body and that defines a reception space capable of receiving the biological tissue,
• the recess includes a bottom that is an innermost part in the radial direction of the expansion body, a proximal-side upright portion extending radially outward from a proximal end of the bottom, and a distal-side upright portion extending radially outward from a distal end of the bottom,
• the plurality of electrode units extend along the proximal-side upright portion or the distal-side upright portion and are spaced apart from each other in a circumferential direction of the expansion body,
• each of the plurality of electrode units includes a bottom-side end located on a side of the bottom of the recess and an outer end located on a side opposite to the bottom-side end in the radial direction of the expansion body, and has a length L extending along the distal-side upright portion or the proximal-side upright portion from the bottom-side end to the outer end, and a width W (mm) orthogonal to the length L (mm), and
• a number N of the electrode units and an average width Wa (mm) that is an average of the widths W (mm) of the plurality of electrode units satisfy the following mathematical expression:
• (
• Wa
• +
• 1
• )
• ×
• N
• 8
• ⁢
• π
• ≥
• 0.4